The Red Hat newlib C Library


• Introduction:
• Stdlib:
• Ctype:
• Stdio:
• Strings:
• Wchar strings:
• Signals:

• Timefns:
• Locale:
• Reentrancy:

• Misc:
• Syscalls:
• Arglists:

• Document Index:

1 Introduction

This reference manual describes the functions provided by the Red Hat “newlib” version of the standard ANSI C library. This document is not intended as an overview or a tutorial for the C library. Each library function is listed with a synopsis of its use, a brief description, return values (including error handling), and portability issues.

Some of the library functions depend on support from the underlying operating system and may not be available on every platform. For embedded systems in particular, many of these underlying operating system services may not be available or may not be fully functional. The specific operating system subroutines required for a particular library function are listed in the “Portability” section of the function description. See Syscalls, for a description of the relevant operating system calls.

2 Standard Utility Functions (`stdlib.h`)

This chapter groups utility functions useful in a variety of programs. The corresponding declarations are in the header file stdlib.h.

• _Exit:		End program execution without cleaning up
• a64l:		String to long long
• abort:		Abnormal termination of a program
• abs:		Integer absolute value (magnitude)
• assert:		Macro for Debugging Diagnostics
• atexit:		Request execution of functions at program exit
• atof:		String to double or float
• atoi:		String to integer
• atoll:		String to long long
• bsearch:		Binary search
• calloc:		Allocate space for arrays
• div:		Divide two integers
• ecvtbuf:		Double or float to string of digits
• ecvt:		Double or float to string of digits (malloc result)
• __env_lock:		Lock environment list for getenv and setenv
• gvcvt:		Format double or float as string
• exit:		End program execution
• getenv:		Look up environment variable
• labs:		Long integer absolute value (magnitude)
• ldiv:		Divide two long integers
• llabs:		Long long integer absolute value (magnitude)
• lldiv:		Divide two long long integers
• malloc:		Allocate and manage memory (malloc, realloc, free)
• mallinfo:		Get information about allocated memory
• __malloc_lock:		Lock memory pool for malloc and free
• mbsrtowcs:		Convert a character string to a wide-character string
• mbstowcs:		Minimal multibyte string to wide string converter
• mblen:		Minimal multibyte length
• mbtowc:		Minimal multibyte to wide character converter
• on_exit:		Request execution of functions at program exit
• qsort:		Array sort
• rand:		Pseudo-random numbers
• rand48:		Uniformly distributed pseudo-random numbers
• strtod:		String to double or float
• strtol:		String to long
• strtoll:		String to long long
• strtoul:		String to unsigned long
• strtoull:		String to unsigned long long
• wcsrtombs:		Convert a wide-character string to a character string
• wcstod:		Wide string to double or float
• wcstol:		Wide string to long
• wcstoll:		Wide string to long long
• wcstoul:		Wide string to unsigned long
• wcstoull:		Wide string to unsigned long long
• system:		Execute command string
• wcstombs:		Minimal wide string to multibyte string converter
• wctomb:		Minimal wide character to multibyte converter

2.1 `_Exit`—end program execution with no cleanup processing

Synopsis

#include <stdlib.h>
void _Exit(int code);

Description
Use _Exit to return control from a program to the host operating environment. Use the argument code to pass an exit status to the operating environment: two particular values, EXIT_SUCCESS and EXIT_FAILURE, are defined in ‘stdlib.h’ to indicate success or failure in a portable fashion.

_Exit differs from exit in that it does not run any application-defined cleanup functions registered with atexit and it does not clean up files and streams. It is identical to _exit.

Returns
_Exit does not return to its caller.

Portability
_Exit is defined by the C99 standard.

Supporting OS subroutines required: _exit.

2.2 `a64l`, `l64a`—convert between radix-64 ASCII string and long

Synopsis

#include <stdlib.h>
long a64l(const char *input);
char *l64a(long input);

Description
Conversion is performed between long and radix-64 characters. The l64a routine transforms up to 32 bits of input value starting from least significant bits to the most significant bits. The input value is split up into a maximum of 5 groups of 6 bits and possibly one group of 2 bits (bits 31 and 30).

Each group of 6 bits forms a value from 0–63 which is translated into a character as follows:

0 = ’.’
1 = ’/’
2–11 = ’0’ to ’9’
12–37 = ’A’ to ’Z’
38–63 = ’a’ to ’z’

When the remaining bits are zero or all bits have been translated, a null terminator is appended to the string. An input value of 0 results in the empty string.

The a64l function performs the reverse translation. Each character is used to generate a 6-bit value for up to 30 bits and then a 2-bit value to complete a 32-bit result. The null terminator means that the remaining digits are 0. An empty input string or NULL string results in 0L. An invalid string results in undefined behavior. If the size of a long is greater than 32 bits, the result is sign-extended.

Returns
l64a returns a null-terminated string of 0 to 6 characters. a64l returns the 32-bit translated value from the input character string.

Portability
l64a and a64l are non-ANSI and are defined by the Single Unix Specification.

Supporting OS subroutines required: None.

2.3 `abort`—abnormal termination of a program

Synopsis

#include <stdlib.h>
void abort(void);

Description
Use abort to signal that your program has detected a condition it cannot deal with. Normally, abort ends your program’s execution.

Before terminating your program, abort raises the exception SIGABRT (using ‘raise(SIGABRT)’). If you have used signal to register an exception handler for this condition, that handler has the opportunity to retain control, thereby avoiding program termination.

In this implementation, abort does not perform any stream- or file-related cleanup (the host environment may do so; if not, you can arrange for your program to do its own cleanup with a SIGABRT exception handler).

Returns
abort does not return to its caller.

Portability
ANSI C requires abort.

Supporting OS subroutines required: _exit and optionally, write.

2.4 `abs`—integer absolute value (magnitude)

Synopsis

#include <stdlib.h>
int abs(int i);

Description
abs returns the absolute value of i (also called the magnitude of i). That is, if i is negative, the result is the opposite of i, but if i is nonnegative the result is i.

The similar function labs uses and returns long rather than int values.

Returns
The result is a nonnegative integer.

Portability
abs is ANSI.

No supporting OS subroutines are required.

2.5 `assert`—macro for debugging diagnostics

Synopsis

#include <assert.h>
void assert(int expression);

Description
Use this macro to embed debuggging diagnostic statements in your programs. The argument expression should be an expression which evaluates to true (nonzero) when your program is working as you intended.

When expression evaluates to false (zero), assert calls abort, after first printing a message showing what failed and where:

 Assertion failed: expression, file filename, line lineno, function: func

If the name of the current function is not known (for example, when using a C89 compiler that does not understand __func__), the function location is omitted.

The macro is defined to permit you to turn off all uses of assert at compile time by defining NDEBUG as a preprocessor variable. If you do this, the assert macro expands to

 (void(0))

Returns
assert does not return a value.

Portability
The assert macro is required by ANSI, as is the behavior when NDEBUG is defined.

Supporting OS subroutines required (only if enabled): close, fstat, getpid, isatty, kill, lseek, read, sbrk, write.

2.6 `atexit`—request execution of functions at program exit

Synopsis

#include <stdlib.h>
int atexit (void (*function)(void));

Description
You can use atexit to enroll functions in a list of functions that will be called when your program terminates normally. The argument is a pointer to a user-defined function (which must not require arguments and must not return a result).

The functions are kept in a LIFO stack; that is, the last function enrolled by atexit will be the first to execute when your program exits.

There is no built-in limit to the number of functions you can enroll in this list; however, after every group of 32 functions is enrolled, atexit will call malloc to get space for the next part of the list. The initial list of 32 functions is statically allocated, so you can always count on at least that many slots available.

Returns
atexit returns 0 if it succeeds in enrolling your function, -1 if it fails (possible only if no space was available for malloc to extend the list of functions).

Portability
atexit is required by the ANSI standard, which also specifies that implementations must support enrolling at least 32 functions.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

2.7 `atof`, `atoff`—string to double or float

Synopsis

#include <stdlib.h>
double atof(const char *s);
float atoff(const char *s);

Description
atof converts the initial portion of a string to a double. atoff converts the initial portion of a string to a float.

The functions parse the character string s, locating a substring which can be converted to a floating-point value. The substring must match the format:

 [+|-]digits[.][digits][(e|E)[+|-]digits]

The substring converted is the longest initial fragment of s that has the expected format, beginning with the first non-whitespace character. The substring is empty if str is empty, consists entirely of whitespace, or if the first non-whitespace character is something other than +, -, ., or a digit.

atof(s) is implemented as strtod(s, NULL). atoff(s) is implemented as strtof(s, NULL).

Returns
atof returns the converted substring value, if any, as a double; or 0.0, if no conversion could be performed. If the correct value is out of the range of representable values, plus or minus HUGE_VAL is returned, and ERANGE is stored in errno. If the correct value would cause underflow, 0.0 is returned and ERANGE is stored in errno.

atoff obeys the same rules as atof, except that it returns a float.

Portability
atof is ANSI C. atof, atoi, and atol are subsumed by strod and strol, but are used extensively in existing code. These functions are less reliable, but may be faster if the argument is verified to be in a valid range.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

2.8 `atoi`, `atol`—string to integer

Synopsis

#include <stdlib.h>
int atoi(const char *s);
long atol(const char *s);
int _atoi_r(struct _reent *ptr, const char *s);
long _atol_r(struct _reent *ptr, const char *s);

Description
atoi converts the initial portion of a string to an int. atol converts the initial portion of a string to a long.

atoi(s) is implemented as (int)strtol(s, NULL, 10). atol(s) is implemented as strtol(s, NULL, 10).

_atoi_r and _atol_r are reentrant versions of atoi and atol respectively, passing the reentrancy struct pointer.

Returns
The functions return the converted value, if any. If no conversion was made, 0 is returned.

Portability
atoi, atol are ANSI.

No supporting OS subroutines are required.

2.9 `atoll`—convert a string to a long long integer

Synopsis

#include <stdlib.h>
long long atoll(const char *str);
long long _atoll_r(struct _reent *ptr, const char *str);

Description
The function atoll converts the initial portion of the string pointed to by *str to a type long long. A call to atoll(str) in this implementation is equivalent to strtoll(str, (char **)NULL, 10) including behavior on error.

The alternate function _atoll_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
The converted value.

Portability
atoll is ISO 9899 (C99) and POSIX 1003.1-2001 compatable.

No supporting OS subroutines are required.

2.10 `bsearch`—binary search

Synopsis

#include <stdlib.h>
void *bsearch(const void *key, const void *base,
    size_t nmemb, size_t size,
    int (*compar)(const void *, const void *));

Description
bsearch searches an array beginning at base for any element that matches key, using binary search. nmemb is the element count of the array; size is the size of each element.

The array must be sorted in ascending order with respect to the comparison function compar (which you supply as the last argument of bsearch).

You must define the comparison function (*compar) to have two arguments; its result must be negative if the first argument is less than the second, zero if the two arguments match, and positive if the first argument is greater than the second (where “less than” and “greater than” refer to whatever arbitrary ordering is appropriate).

Returns
Returns a pointer to an element of array that matches key. If more than one matching element is available, the result may point to any of them.

Portability
bsearch is ANSI.

No supporting OS subroutines are required.

2.11 `calloc`—allocate space for arrays

Synopsis

#include <stdlib.h>
void *calloc(size_t n, size_t s);
void *_calloc_r(void *reent, size_t n, size_t s);

Description
Use calloc to request a block of memory sufficient to hold an array of n elements, each of which has size s.

The memory allocated by calloc comes out of the same memory pool used by malloc, but the memory block is initialized to all zero bytes. (To avoid the overhead of initializing the space, use malloc instead.)

The alternate function _calloc_r is reentrant. The extra argument reent is a pointer to a reentrancy structure.

Returns
If successful, a pointer to the newly allocated space.

If unsuccessful, NULL.

Portability
calloc is ANSI.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

2.12 `div`—divide two integers

Synopsis

#include <stdlib.h>
div_t div(int n, int d);

Description
Divide n/d, returning quotient and remainder as two integers in a structure div_t.

Returns
The result is represented with the structure

 typedef struct
 {
  int quot;
  int rem;
 } div_t;

where the quot field represents the quotient, and rem the remainder. For nonzero d, if ‘r = div(n,d);’ then n equals ‘r.rem + d*r.quot’.

To divide long rather than int values, use the similar function ldiv.

Portability
div is ANSI.

No supporting OS subroutines are required.

2.13 `ecvt`, `ecvtf`, `fcvt`, `fcvtf`—double or float to string

Synopsis

#include <stdlib.h>

char *ecvt(double val, int chars, int *decpt, int *sgn);
char *ecvtf(float val, int chars, int *decpt, int *sgn);

char *fcvt(double val, int decimals, 
    int *decpt, int *sgn);
char *fcvtf(float val, int decimals, 
    int *decpt, int *sgn);

Description
ecvt and fcvt produce (null-terminated) strings of digits representating the double number val. ecvtf and fcvtf produce the corresponding character representations of float numbers.

(The stdlib functions ecvtbuf and fcvtbuf are reentrant versions of ecvt and fcvt.)

The only difference between ecvt and fcvt is the interpretation of the second argument (chars or decimals). For ecvt, the second argument chars specifies the total number of characters to write (which is also the number of significant digits in the formatted string, since these two functions write only digits). For fcvt, the second argument decimals specifies the number of characters to write after the decimal point; all digits for the integer part of val are always included.

Since ecvt and fcvt write only digits in the output string, they record the location of the decimal point in *decpt, and the sign of the number in *sgn. After formatting a number, *decpt contains the number of digits to the left of the decimal point. *sgn contains 0 if the number is positive, and 1 if it is negative.

Returns
All four functions return a pointer to the new string containing a character representation of val.

Portability
None of these functions are ANSI C.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

2.14 `gvcvt`, `gcvtf`—format double or float as string

Synopsis

#include <stdlib.h>

char *gcvt(double val, int precision, char *buf);
char *gcvtf(float val, int precision, char *buf);

Description
gcvt writes a fully formatted number as a null-terminated string in the buffer *buf. gdvtf produces corresponding character representations of float numbers.

gcvt uses the same rules as the printf format ‘%.precisiong’—only negative values are signed (with ‘-’), and either exponential or ordinary decimal-fraction format is chosen depending on the number of significant digits (specified by precision).

Returns
The result is a pointer to the formatted representation of val (the same as the argument buf).

Portability
Neither function is ANSI C.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

2.15 `ecvtbuf`, `fcvtbuf`—double or float to string

Synopsis

#include <stdio.h>

char *ecvtbuf(double val, int chars, int *decpt,
    int *sgn, char *buf);

char *fcvtbuf(double val, int decimals, int *decpt,
    int *sgn, char *buf);

Description
ecvtbuf and fcvtbuf produce (null-terminated) strings of digits representating the double number val.

The only difference between ecvtbuf and fcvtbuf is the interpretation of the second argument (chars or decimals). For ecvtbuf, the second argument chars specifies the total number of characters to write (which is also the number of significant digits in the formatted string, since these two functions write only digits). For fcvtbuf, the second argument decimals specifies the number of characters to write after the decimal point; all digits for the integer part of val are always included.

Since ecvtbuf and fcvtbuf write only digits in the output string, they record the location of the decimal point in *decpt, and the sign of the number in *sgn. After formatting a number, *decpt contains the number of digits to the left of the decimal point. *sgn contains 0 if the number is positive, and 1 if it is negative. For both functions, you supply a pointer buf to an area of memory to hold the converted string.

Returns
Both functions return a pointer to buf, the string containing a character representation of val.

Portability
Neither function is ANSI C.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

2.16 `__env_lock`, `__env_unlock`—lock environ variable

Synopsis

#include <envlock.h>
void __env_lock (struct _reent *reent);
void __env_unlock (struct _reent *reent);

Description
The setenv family of routines call these functions when they need to modify the environ variable. The version of these routines supplied in the library use the lock API defined in sys/lock.h. If multiple threads of execution can call setenv, or if setenv can be called reentrantly, then you need to define your own versions of these functions in order to safely lock the memory pool during a call. If you do not, the memory pool may become corrupted.

A call to setenv may call __env_lock recursively; that is, the sequence of calls may go __env_lock, __env_lock, __env_unlock, __env_unlock. Any implementation of these routines must be careful to avoid causing a thread to wait for a lock that it already holds.

2.17 `exit`—end program execution

Synopsis

#include <stdlib.h>
void exit(int code);

Description
Use exit to return control from a program to the host operating environment. Use the argument code to pass an exit status to the operating environment: two particular values, EXIT_SUCCESS and EXIT_FAILURE, are defined in ‘stdlib.h’ to indicate success or failure in a portable fashion.

exit does two kinds of cleanup before ending execution of your program. First, it calls all application-defined cleanup functions you have enrolled with atexit. Second, files and streams are cleaned up: any pending output is delivered to the host system, each open file or stream is closed, and files created by tmpfile are deleted.

Returns
exit does not return to its caller.

Portability
ANSI C requires exit, and specifies that EXIT_SUCCESS and EXIT_FAILURE must be defined.

Supporting OS subroutines required: _exit.

2.18 `getenv`—look up environment variable

Synopsis

#include <stdlib.h>
char *getenv(const char *name);

Description
getenv searches the list of environment variable names and values (using the global pointer “char **environ”) for a variable whose name matches the string at name. If a variable name matches, getenv returns a pointer to the associated value.

Returns
A pointer to the (string) value of the environment variable, or NULL if there is no such environment variable.

Portability
getenv is ANSI, but the rules for properly forming names of environment variables vary from one system to another.

getenv requires a global pointer environ.

2.19 `labs`—long integer absolute value

Synopsis

#include <stdlib.h>
long labs(long i);

Description
labs returns the absolute value of i (also called the magnitude of i). That is, if i is negative, the result is the opposite of i, but if i is nonnegative the result is i.

The similar function abs uses and returns int rather than long values.

Returns
The result is a nonnegative long integer.

Portability
labs is ANSI.

No supporting OS subroutine calls are required.

2.20 `ldiv`—divide two long integers

Synopsis

#include <stdlib.h>
ldiv_t ldiv(long n, long d);

Description
Divide n/d, returning quotient and remainder as two long integers in a structure ldiv_t.

Returns
The result is represented with the structure

 typedef struct
 {
  long quot;
  long rem;
 } ldiv_t;

where the quot field represents the quotient, and rem the remainder. For nonzero d, if ‘r = ldiv(n,d);’ then n equals ‘r.rem + d*r.quot’.

To divide int rather than long values, use the similar function div.

Portability
ldiv is ANSI.

No supporting OS subroutines are required.

2.21 `llabs`—compute the absolute value of an long long integer.

Synopsis

#include <stdlib.h>
long long llabs(long long j);

Description
The llabs function computes the absolute value of the long long integer argument j (also called the magnitude of j).

The similar function labs uses and returns long rather than long long values.

Returns
A nonnegative long long integer.

Portability
llabs is ISO 9899 (C99) compatable.

No supporting OS subroutines are required.

2.22 `lldiv`—divide two long long integers

Synopsis

#include <stdlib.h>
lldiv_t lldiv(long long n, long long d);

Description
Divide n/d, returning quotient and remainder as two long long integers in a structure lldiv_t.

Returns
The result is represented with the structure

 typedef struct
 {
  long long quot;
  long long rem;
 } lldiv_t;

where the quot field represents the quotient, and rem the remainder. For nonzero d, if ‘r = ldiv(n,d);’ then n equals ‘r.rem + d*r.quot’.

To divide long rather than long long values, use the similar function ldiv.

Portability
lldiv is ISO 9899 (C99) compatable.

No supporting OS subroutines are required.

2.23 `malloc`, `realloc`, `free`—manage memory

Synopsis

#include <stdlib.h>
void *malloc(size_t nbytes);
void *realloc(void *aptr, size_t nbytes);
void *reallocf(void *aptr, size_t nbytes);
void free(void *aptr);

void *memalign(size_t align, size_t nbytes);

size_t malloc_usable_size(void *aptr);

void *_malloc_r(void *reent, size_t nbytes);
void *_realloc_r(void *reent, 
    void *aptr, size_t nbytes);
void *_reallocf_r(void *reent, 
    void *aptr, size_t nbytes);
void _free_r(void *reent, void *aptr);

void *_memalign_r(void *reent,
    size_t align, size_t nbytes);

size_t _malloc_usable_size_r(void *reent, void *aptr);

Description
These functions manage a pool of system memory.

Use malloc to request allocation of an object with at least nbytes bytes of storage available. If the space is available, malloc returns a pointer to a newly allocated block as its result.

If you already have a block of storage allocated by malloc, but you no longer need all the space allocated to it, you can make it smaller by calling realloc with both the object pointer and the new desired size as arguments. realloc guarantees that the contents of the smaller object match the beginning of the original object.

Similarly, if you need more space for an object, use realloc to request the larger size; again, realloc guarantees that the beginning of the new, larger object matches the contents of the original object.

When you no longer need an object originally allocated by malloc or realloc (or the related function calloc), return it to the memory storage pool by calling free with the address of the object as the argument. You can also use realloc for this purpose by calling it with 0 as the nbytes argument.

The reallocf function behaves just like realloc except if the function is required to allocate new storage and this fails. In this case reallocf will free the original object passed in whereas realloc will not.

The memalign function returns a block of size nbytes aligned to a align boundary. The align argument must be a power of two.

The malloc_usable_size function takes a pointer to a block allocated by malloc. It returns the amount of space that is available in the block. This may or may not be more than the size requested from malloc, due to alignment or minimum size constraints.

The alternate functions _malloc_r, _realloc_r, _reallocf_r, _free_r, _memalign_r, and _malloc_usable_size_r are reentrant versions. The extra argument reent is a pointer to a reentrancy structure.

If you have multiple threads of execution which may call any of these routines, or if any of these routines may be called reentrantly, then you must provide implementations of the __malloc_lock and __malloc_unlock functions for your system. See the documentation for those functions.

These functions operate by calling the function _sbrk_r or sbrk, which allocates space. You may need to provide one of these functions for your system. _sbrk_r is called with a positive value to allocate more space, and with a negative value to release previously allocated space if it is no longer required. See Stubs.

Returns
malloc returns a pointer to the newly allocated space, if successful; otherwise it returns NULL. If your application needs to generate empty objects, you may use malloc(0) for this purpose.

realloc returns a pointer to the new block of memory, or NULL if a new block could not be allocated. NULL is also the result when you use ‘realloc(aptr,0)’ (which has the same effect as ‘free(aptr)’). You should always check the result of realloc; successful reallocation is not guaranteed even when you request a smaller object.

free does not return a result.

memalign returns a pointer to the newly allocated space.

malloc_usable_size returns the usable size.

Portability
malloc, realloc, and free are specified by the ANSI C standard, but other conforming implementations of malloc may behave differently when nbytes is zero.

memalign is part of SVR4.

malloc_usable_size is not portable.

Supporting OS subroutines required: sbrk.

2.24 `mallinfo`, `malloc_stats`, `mallopt`—malloc support

Synopsis

#include <malloc.h>
struct mallinfo mallinfo(void);
void malloc_stats(void);
int mallopt(int parameter, value);

struct mallinfo _mallinfo_r(void *reent);
void _malloc_stats_r(void *reent);
int _mallopt_r(void *reent, int parameter, value);

Description
mallinfo returns a structure describing the current state of memory allocation. The structure is defined in malloc.h. The following fields are defined: arena is the total amount of space in the heap; ordblks is the number of chunks which are not in use; uordblks is the total amount of space allocated by malloc; fordblks is the total amount of space not in use; keepcost is the size of the top most memory block.

malloc_stats print some statistics about memory allocation on standard error.

mallopt takes a parameter and a value. The parameters are defined in malloc.h, and may be one of the following: M_TRIM_THRESHOLD sets the maximum amount of unused space in the top most block before releasing it back to the system in free (the space is released by calling _sbrk_r with a negative argument); M_TOP_PAD is the amount of padding to allocate whenever _sbrk_r is called to allocate more space.

The alternate functions _mallinfo_r, _malloc_stats_r, and _mallopt_r are reentrant versions. The extra argument reent is a pointer to a reentrancy structure.

Returns
mallinfo returns a mallinfo structure. The structure is defined in malloc.h.

malloc_stats does not return a result.

mallopt returns zero if the parameter could not be set, or non-zero if it could be set.

Portability
mallinfo and mallopt are provided by SVR4, but mallopt takes different parameters on different systems. malloc_stats is not portable.

2.25 `__malloc_lock`, `__malloc_unlock`—lock malloc pool

Synopsis

#include <malloc.h>
void __malloc_lock (struct _reent *reent);
void __malloc_unlock (struct _reent *reent);

Description
The malloc family of routines call these functions when they need to lock the memory pool. The version of these routines supplied in the library use the lock API defined in sys/lock.h. If multiple threads of execution can call malloc, or if malloc can be called reentrantly, then you need to define your own versions of these functions in order to safely lock the memory pool during a call. If you do not, the memory pool may become corrupted.

A call to malloc may call __malloc_lock recursively; that is, the sequence of calls may go __malloc_lock, __malloc_lock, __malloc_unlock, __malloc_unlock. Any implementation of these routines must be careful to avoid causing a thread to wait for a lock that it already holds.

2.26 `mblen`—minimal multibyte length function

Synopsis

#include <stdlib.h>
int mblen(const char *s, size_t n);

Description
When _MB_CAPABLE is not defined, this is a minimal ANSI-conforming implementation of mblen. In this case, the only “multi-byte character sequences” recognized are single bytes, and thus 1 is returned unless s is the null pointer or has a length of 0 or is the empty string.

When _MB_CAPABLE is defined, this routine calls _mbtowc_r to perform the conversion, passing a state variable to allow state dependent decoding. The result is based on the locale setting which may be restricted to a defined set of locales.

Returns
This implementation of mblen returns 0 if s is NULL or the empty string; it returns 1 if not _MB_CAPABLE or the character is a single-byte character; it returns -1 if the multi-byte character is invalid; otherwise it returns the number of bytes in the multibyte character.

Portability
mblen is required in the ANSI C standard. However, the precise effects vary with the locale.

mblen requires no supporting OS subroutines.

2.27 `mbsrtowcs`, `mbsnrtowcs`—convert a character string to a wide-character string

Synopsis

#include <wchar.h>
size_t mbsrtowcs(wchar_t *__restrict dst,
    const char **__restrict src,
    size_t len,
    mbstate_t *__restrict ps);

#include <wchar.h>
size_t _mbsrtowcs_r(struct _reent *ptr, wchar_t *dst,
    const char **src, size_t len,
    mbstate_t *ps);

#include <wchar.h>
size_t mbsnrtowcs(wchar_t *__ restrict dst, 
    const char **__restrict src, size_t nms,
    size_t len, mbstate_t *__restrict ps);

#include <wchar.h>
size_t _mbsnrtowcs_r(struct _reent *ptr, wchar_t *dst,
    const char **src, size_t nms,
    size_t len, mbstate_t *ps);

Description
The mbsrtowcs function converts a sequence of multibyte characters pointed to indirectly by src into a sequence of corresponding wide characters and stores at most len of them in the wchar_t array pointed to by dst, until it encounters a terminating null character (’\0’).

If dst is NULL, no characters are stored.

If dst is not NULL, the pointer pointed to by src is updated to point to the character after the one that conversion stopped at. If conversion stops because a null character is encountered, *src is set to NULL.

The mbstate_t argument, ps, is used to keep track of the shift state. If it is NULL, mbsrtowcs uses an internal, static mbstate_t object, which is initialized to the initial conversion state at program startup.

The mbsnrtowcs function behaves identically to mbsrtowcs, except that conversion stops after reading at most nms bytes from the buffer pointed to by src.

Returns
The mbsrtowcs and mbsnrtowcs functions return the number of wide characters stored in the array pointed to by dst if successful, otherwise it returns (size_t)-1.

Portability
mbsrtowcs is defined by the C99 standard. mbsnrtowcs is defined by the POSIX.1-2008 standard.

2.28 `mbstowcs`—minimal multibyte string to wide char converter

Synopsis

#include <stdlib.h>
int mbstowcs(wchar_t *restrict pwc, const char *restrict s, size_t n);

Description
When _MB_CAPABLE is not defined, this is a minimal ANSI-conforming implementation of mbstowcs. In this case, the only “multi-byte character sequences” recognized are single bytes, and they are “converted” to wide-char versions simply by byte extension.

When _MB_CAPABLE is defined, this routine calls _mbstowcs_r to perform the conversion, passing a state variable to allow state dependent decoding. The result is based on the locale setting which may be restricted to a defined set of locales.

Returns
This implementation of mbstowcs returns 0 if s is NULL or is the empty string; it returns -1 if _MB_CAPABLE and one of the multi-byte characters is invalid or incomplete; otherwise it returns the minimum of: n or the number of multi-byte characters in s plus 1 (to compensate for the nul character). If the return value is -1, the state of the pwc string is indeterminate. If the input has a length of 0, the output string will be modified to contain a wchar_t nul terminator.

Portability
mbstowcs is required in the ANSI C standard. However, the precise effects vary with the locale.

mbstowcs requires no supporting OS subroutines.

2.29 `mbtowc`—minimal multibyte to wide char converter

Synopsis

#include <stdlib.h>
int mbtowc(wchar_t *restrict pwc, const char *restrict s, size_t n);

Description
When _MB_CAPABLE is not defined, this is a minimal ANSI-conforming implementation of mbtowc. In this case, only “multi-byte character sequences” recognized are single bytes, and they are “converted” to themselves. Each call to mbtowc copies one character from *s to *pwc, unless s is a null pointer. The argument n is ignored.

Returns
This implementation of mbtowc returns 0 if s is NULL or is the empty string; it returns 1 if not _MB_CAPABLE or the character is a single-byte character; it returns -1 if n is 0 or the multi-byte character is invalid; otherwise it returns the number of bytes in the multibyte character. If the return value is -1, no changes are made to the pwc output string. If the input is the empty string, a wchar_t nul is placed in the output string and 0 is returned. If the input has a length of 0, no changes are made to the pwc output string.

Portability
mbtowc is required in the ANSI C standard. However, the precise effects vary with the locale.

mbtowc requires no supporting OS subroutines.

2.30 `on_exit`—request execution of function with argument at program exit

Synopsis

#include <stdlib.h>
int on_exit (void (*function)(int, void *), void *arg);

Description
You can use on_exit to enroll functions in a list of functions that will be called when your program terminates normally. The argument is a pointer to a user-defined function which takes two arguments. The first is the status code passed to exit and the second argument is of type pointer to void. The function must not return a result. The value of arg is registered and passed as the argument to function.

The functions are kept in a LIFO stack; that is, the last function enrolled by atexit or on_exit will be the first to execute when your program exits. You can intermix functions using atexit and on_exit.

There is no built-in limit to the number of functions you can enroll in this list; however, after every group of 32 functions is enrolled, atexit/on_exit will call malloc to get space for the next part of the list. The initial list of 32 functions is statically allocated, so you can always count on at least that many slots available.

Returns
on_exit returns 0 if it succeeds in enrolling your function, -1 if it fails (possible only if no space was available for malloc to extend the list of functions).

Portability
on_exit is a non-standard glibc extension

Supporting OS subroutines required: None

2.31 `qsort`—sort an array

Synopsis

#include <stdlib.h>
void qsort(void *base, size_t nmemb, size_t size,
    int (*compar)(const void *, const void *) );

Description
qsort sorts an array (beginning at base) of nmemb objects. size describes the size of each element of the array.

You must supply a pointer to a comparison function, using the argument shown as compar. (This permits sorting objects of unknown properties.) Define the comparison function to accept two arguments, each a pointer to an element of the array starting at base. The result of (*compar) must be negative if the first argument is less than the second, zero if the two arguments match, and positive if the first argument is greater than the second (where “less than” and “greater than” refer to whatever arbitrary ordering is appropriate).

The array is sorted in place; that is, when qsort returns, the array elements beginning at base have been reordered.

Returns
qsort does not return a result.

Portability
qsort is required by ANSI (without specifying the sorting algorithm).

2.32 `rand`, `srand`—pseudo-random numbers

Synopsis

#include <stdlib.h>
int rand(void);
void srand(unsigned int seed);
int rand_r(unsigned int *seed);

Description
rand returns a different integer each time it is called; each integer is chosen by an algorithm designed to be unpredictable, so that you can use rand when you require a random number. The algorithm depends on a static variable called the “random seed”; starting with a given value of the random seed always produces the same sequence of numbers in successive calls to rand.

You can set the random seed using srand; it does nothing beyond storing its argument in the static variable used by rand. You can exploit this to make the pseudo-random sequence less predictable, if you wish, by using some other unpredictable value (often the least significant parts of a time-varying value) as the random seed before beginning a sequence of calls to rand; or, if you wish to ensure (for example, while debugging) that successive runs of your program use the same “random” numbers, you can use srand to set the same random seed at the outset.

Returns
rand returns the next pseudo-random integer in sequence; it is a number between 0 and RAND_MAX (inclusive).

srand does not return a result.

Portability
rand is required by ANSI, but the algorithm for pseudo-random number generation is not specified; therefore, even if you use the same random seed, you cannot expect the same sequence of results on two different systems.

rand requires no supporting OS subroutines.

2.33 `rand48`, `drand48`, `erand48`, `lrand48`, `nrand48`, `mrand48`, `jrand48`, `srand48`, `seed48`, `lcong48`—pseudo-random number generators and initialization routines

Synopsis

#include <stdlib.h>
double drand48(void);
double erand48(unsigned short xseed[3]);
long lrand48(void);
long nrand48(unsigned short xseed[3]);
long mrand48(void);
long jrand48(unsigned short xseed[3]);
void srand48(long seed);
unsigned short *seed48(unsigned short xseed[3]);
void lcong48(unsigned short p[7]);

Description
The rand48 family of functions generates pseudo-random numbers using a linear congruential algorithm working on integers 48 bits in size. The particular formula employed is r(n+1) = (a * r(n) + c) mod m where the default values are for the multiplicand a = 0xfdeece66d = 25214903917 and the addend c = 0xb = 11. The modulo is always fixed at m = 2 ** 48. r(n) is called the seed of the random number generator.

For all the six generator routines described next, the first computational step is to perform a single iteration of the algorithm.

drand48 and erand48 return values of type double. The full 48 bits of r(n+1) are loaded into the mantissa of the returned value, with the exponent set such that the values produced lie in the interval [0.0, 1.0].

lrand48 and nrand48 return values of type long in the range [0, 2**31-1]. The high-order (31) bits of r(n+1) are loaded into the lower bits of the returned value, with the topmost (sign) bit set to zero.

mrand48 and jrand48 return values of type long in the range [-2**31, 2**31-1]. The high-order (32) bits of r(n+1) are loaded into the returned value.

drand48, lrand48, and mrand48 use an internal buffer to store r(n). For these functions the initial value of r(0) = 0x1234abcd330e = 20017429951246.

On the other hand, erand48, nrand48, and jrand48 use a user-supplied buffer to store the seed r(n), which consists of an array of 3 shorts, where the zeroth member holds the least significant bits.

All functions share the same multiplicand and addend.

srand48 is used to initialize the internal buffer r(n) of drand48, lrand48, and mrand48 such that the 32 bits of the seed value are copied into the upper 32 bits of r(n), with the lower 16 bits of r(n) arbitrarily being set to 0x330e. Additionally, the constant multiplicand and addend of the algorithm are reset to the default values given above.

seed48 also initializes the internal buffer r(n) of drand48, lrand48, and mrand48, but here all 48 bits of the seed can be specified in an array of 3 shorts, where the zeroth member specifies the lowest bits. Again, the constant multiplicand and addend of the algorithm are reset to the default values given above. seed48 returns a pointer to an array of 3 shorts which contains the old seed. This array is statically allocated, thus its contents are lost after each new call to seed48.

Finally, lcong48 allows full control over the multiplicand and addend used in drand48, erand48, lrand48, nrand48, mrand48, and jrand48, and the seed used in drand48, lrand48, and mrand48. An array of 7 shorts is passed as parameter; the first three shorts are used to initialize the seed; the second three are used to initialize the multiplicand; and the last short is used to initialize the addend. It is thus not possible to use values greater than 0xffff as the addend.

Note that all three methods of seeding the random number generator always also set the multiplicand and addend for any of the six generator calls.

For a more powerful random number generator, see random.

Portability
SUS requires these functions.

No supporting OS subroutines are required.

2.34 `strtod`, `strtof`—string to double or float

Synopsis

#include <stdlib.h>
double strtod(const char *restrict str, char **restrict tail);
float strtof(const char *restrict str, char **restrict tail);

double _strtod_r(void *reent,
    const char *restrict str, char **restrict tail);

Description
The function strtod parses the character string str, producing a substring which can be converted to a double value. The substring converted is the longest initial subsequence of str, beginning with the first non-whitespace character, that has one of these formats:

[+|-]digits[.[digits]][(e|E)[+|-]digits]
[+|-].digits[(e|E)[+|-]digits]
[+|-](i|I)(n|N)(f|F)[(i|I)(n|N)(i|I)(t|T)(y|Y)]
[+|-](n|N)(a|A)(n|N)[<(>[hexdigits]<)>]
[+|-]0(x|X)hexdigits[.[hexdigits]][(p|P)[+|-]digits]
[+|-]0(x|X).hexdigits[(p|P)[+|-]digits]

The substring contains no characters if str is empty, consists entirely of whitespace, or if the first non-whitespace character is something other than +, -, ., or a digit, and cannot be parsed as infinity or NaN. If the platform does not support NaN, then NaN is treated as an empty substring. If the substring is empty, no conversion is done, and the value of str is stored in *tail. Otherwise, the substring is converted, and a pointer to the final string (which will contain at least the terminating null character of str) is stored in *tail. If you want no assignment to *tail, pass a null pointer as tail. strtof is identical to strtod except for its return type.

This implementation returns the nearest machine number to the input decimal string. Ties are broken by using the IEEE round-even rule. However, strtof is currently subject to double rounding errors.

The alternate function _strtod_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
strtod returns the converted substring value, if any. If no conversion could be performed, 0 is returned. If the correct value is out of the range of representable values, plus or minus HUGE_VAL is returned, and ERANGE is stored in errno. If the correct value would cause underflow, 0 is returned and ERANGE is stored in errno.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

2.35 `strtol`—string to long

Synopsis

#include <stdlib.h>
long strtol(const char *restrict s, char **restrict ptr,int base);

long _strtol_r(void *reent, 
    const char *restrict s, char **restrict ptr,int base);

Description
The function strtol converts the string *s to a long. First, it breaks down the string into three parts: leading whitespace, which is ignored; a subject string consisting of characters resembling an integer in the radix specified by base; and a trailing portion consisting of zero or more unparseable characters, and always including the terminating null character. Then, it attempts to convert the subject string into a long and returns the result.

If the value of base is 0, the subject string is expected to look like a normal C integer constant: an optional sign, a possible ‘0x’ indicating a hexadecimal base, and a number. If base is between 2 and 36, the expected form of the subject is a sequence of letters and digits representing an integer in the radix specified by base, with an optional plus or minus sign. The letters a–z (or, equivalently, A–Z) are used to signify values from 10 to 35; only letters whose ascribed values are less than base are permitted. If base is 16, a leading 0x is permitted.

The subject sequence is the longest initial sequence of the input string that has the expected form, starting with the first non-whitespace character. If the string is empty or consists entirely of whitespace, or if the first non-whitespace character is not a permissible letter or digit, the subject string is empty.

If the subject string is acceptable, and the value of base is zero, strtol attempts to determine the radix from the input string. A string with a leading 0x is treated as a hexadecimal value; a string with a leading 0 and no x is treated as octal; all other strings are treated as decimal. If base is between 2 and 36, it is used as the conversion radix, as described above. If the subject string begins with a minus sign, the value is negated. Finally, a pointer to the first character past the converted subject string is stored in ptr, if ptr is not NULL.

If the subject string is empty (or not in acceptable form), no conversion is performed and the value of s is stored in ptr (if ptr is not NULL).

The alternate function _strtol_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
strtol returns the converted value, if any. If no conversion was made, 0 is returned.

strtol returns LONG_MAX or LONG_MIN if the magnitude of the converted value is too large, and sets errno to ERANGE.

Portability
strtol is ANSI.

No supporting OS subroutines are required.

2.36 `strtoll`—string to long long

Synopsis

#include <stdlib.h>
long long strtoll(const char *restrict s, char **restrict ptr,int base);

long long _strtoll_r(void *reent, 
    const char *restrict s, char **restrict ptr,int base);

Description
The function strtoll converts the string *s to a long long. First, it breaks down the string into three parts: leading whitespace, which is ignored; a subject string consisting of characters resembling an integer in the radix specified by base; and a trailing portion consisting of zero or more unparseable characters, and always including the terminating null character. Then, it attempts to convert the subject string into a long long and returns the result.

If the subject string is acceptable, and the value of base is zero, strtoll attempts to determine the radix from the input string. A string with a leading 0x is treated as a hexadecimal value; a string with a leading 0 and no x is treated as octal; all other strings are treated as decimal. If base is between 2 and 36, it is used as the conversion radix, as described above. If the subject string begins with a minus sign, the value is negated. Finally, a pointer to the first character past the converted subject string is stored in ptr, if ptr is not NULL.

If the subject string is empty (or not in acceptable form), no conversion is performed and the value of s is stored in ptr (if ptr is not NULL).

The alternate function _strtoll_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
strtoll returns the converted value, if any. If no conversion was made, 0 is returned.

strtoll returns LONG_LONG_MAX or LONG_LONG_MIN if the magnitude of the converted value is too large, and sets errno to ERANGE.

Portability
strtoll is ANSI.

No supporting OS subroutines are required.

2.37 `strtoul`—string to unsigned long

Synopsis

#include <stdlib.h>
unsigned long strtoul(const char *restrict s, char **restrict ptr,
    int base);

unsigned long _strtoul_r(void *reent, const char *restrict s,
    char **restrict ptr, int base);

Description
The function strtoul converts the string *s to an unsigned long. First, it breaks down the string into three parts: leading whitespace, which is ignored; a subject string consisting of the digits meaningful in the radix specified by base (for example, 0 through 7 if the value of base is 8); and a trailing portion consisting of one or more unparseable characters, which always includes the terminating null character. Then, it attempts to convert the subject string into an unsigned long integer, and returns the result.

If the value of base is zero, the subject string is expected to look like a normal C integer constant (save that no optional sign is permitted): a possible 0x indicating hexadecimal radix, and a number. If base is between 2 and 36, the expected form of the subject is a sequence of digits (which may include letters, depending on the base) representing an integer in the radix specified by base. The letters a–z (or A–Z) are used as digits valued from 10 to 35. If base is 16, a leading 0x is permitted.

If the subject string is acceptable, and the value of base is zero, strtoul attempts to determine the radix from the input string. A string with a leading 0x is treated as a hexadecimal value; a string with a leading 0 and no x is treated as octal; all other strings are treated as decimal. If base is between 2 and 36, it is used as the conversion radix, as described above. Finally, a pointer to the first character past the converted subject string is stored in ptr, if ptr is not NULL.

If the subject string is empty (that is, if *s does not start with a substring in acceptable form), no conversion is performed and the value of s is stored in ptr (if ptr is not NULL).

The alternate function _strtoul_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
strtoul returns the converted value, if any. If no conversion was made, 0 is returned.

strtoul returns ULONG_MAX if the magnitude of the converted value is too large, and sets errno to ERANGE.

Portability
strtoul is ANSI.

strtoul requires no supporting OS subroutines.

2.38 `strtoull`—string to unsigned long long

Synopsis

#include <stdlib.h>
unsigned long long strtoull(const char *restrict s, char **restrict ptr,
    int base);

unsigned long long _strtoull_r(void *reent, const char *restrict s,
    char **restrict ptr, int base);

Description
The function strtoull converts the string *s to an unsigned long long. First, it breaks down the string into three parts: leading whitespace, which is ignored; a subject string consisting of the digits meaningful in the radix specified by base (for example, 0 through 7 if the value of base is 8); and a trailing portion consisting of one or more unparseable characters, which always includes the terminating null character. Then, it attempts to convert the subject string into an unsigned long long integer, and returns the result.

If the subject string is acceptable, and the value of base is zero, strtoull attempts to determine the radix from the input string. A string with a leading 0x is treated as a hexadecimal value; a string with a leading 0 and no x is treated as octal; all other strings are treated as decimal. If base is between 2 and 36, it is used as the conversion radix, as described above. Finally, a pointer to the first character past the converted subject string is stored in ptr, if ptr is not NULL.

If the subject string is empty (that is, if *s does not start with a substring in acceptable form), no conversion is performed and the value of s is stored in ptr (if ptr is not NULL).

The alternate function _strtoull_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
strtoull returns the converted value, if any. If no conversion was made, 0 is returned.

strtoull returns ULONG_LONG_MAX if the magnitude of the converted value is too large, and sets errno to ERANGE.

Portability
strtoull is ANSI.

strtoull requires no supporting OS subroutines.

2.39 `wcsrtombs`, `wcsnrtombs`—convert a wide-character string to a character string

Synopsis

#include <wchar.h>
size_t wcsrtombs(char *__restrict dst,
    const wchar_t **__restrict src, size_t len,
    mbstate_t *__restrict ps);

#include <wchar.h>
size_t _wcsrtombs_r(struct _reent *ptr, char *dst,
    const wchar_t **src, size_t len,
    mbstate_t *ps);

#include <wchar.h>
size_t wcsnrtombs(char *__restrict dst,
    const wchar_t **__restrict src,
    size_t nwc, size_t len,
    mbstate_t *__restrict ps);

#include <wchar.h>
size_t _wcsnrtombs_r(struct _reent *ptr, char *dst,
    const wchar_t **src, size_t nwc,
    size_t len, mbstate_t *ps);

Description
The wcsrtombs function converts a string of wide characters indirectly pointed to by src to a corresponding multibyte character string stored in the array pointed to by dst>. No more than len bytes are written to dst>.

If dst> is NULL, no characters are stored.

If dst> is not NULL, the pointer pointed to by src is updated to point to the character after the one that conversion stopped at. If conversion stops because a null character is encountered, *src is set to NULL.

The mbstate_t argument, ps, is used to keep track of the shift state. If it is NULL, wcsrtombs uses an internal, static mbstate_t object, which is initialized to the initial conversion state at program startup.

The wcsnrtombs function behaves identically to wcsrtombs, except that conversion stops after reading at most nwc characters from the buffer pointed to by src.

Returns
The wcsrtombs and wcsnrtombs functions return the number of bytes stored in the array pointed to by dst (not including any terminating null), if successful, otherwise it returns (size_t)-1.

Portability
wcsrtombs is defined by C99 standard. wcsnrtombs is defined by the POSIX.1-2008 standard.

2.40 `wcstod`, `wcstof`—wide char string to double or float

Synopsis

#include <stdlib.h>
double wcstod(const wchar_t *__restrict str,
    wchar_t **__restrict tail);
float wcstof(const wchar_t *__restrict str,
    wchar_t **__restrict tail);

double _wcstod_r(void *reent,
    const wchar_t *str, wchar_t **tail);
float _wcstof_r(void *reent,
    const wchar_t *str, wchar_t **tail);

Description
The function wcstod parses the wide character string str, producing a substring which can be converted to a double value. The substring converted is the longest initial subsequence of str, beginning with the first non-whitespace character, that has one of these formats:

[+|-]digits[.[digits]][(e|E)[+|-]digits]
[+|-].digits[(e|E)[+|-]digits]
[+|-](i|I)(n|N)(f|F)[(i|I)(n|N)(i|I)(t|T)(y|Y)]
[+|-](n|N)(a|A)(n|N)[<(>[hexdigits]<)>]
[+|-]0(x|X)hexdigits[.[hexdigits]][(p|P)[+|-]digits]
[+|-]0(x|X).hexdigits[(p|P)[+|-]digits]

The substring contains no characters if str is empty, consists entirely of whitespace, or if the first non-whitespace character is something other than +, -, ., or a digit, and cannot be parsed as infinity or NaN. If the platform does not support NaN, then NaN is treated as an empty substring. If the substring is empty, no conversion is done, and the value of str is stored in *tail. Otherwise, the substring is converted, and a pointer to the final string (which will contain at least the terminating null character of str) is stored in *tail. If you want no assignment to *tail, pass a null pointer as tail. wcstof is identical to wcstod except for its return type.

This implementation returns the nearest machine number to the input decimal string. Ties are broken by using the IEEE round-even rule. However, wcstof is currently subject to double rounding errors.

The alternate functions _wcstod_r and _wcstof_r are reentrant versions of wcstod and wcstof, respectively. The extra argument reent is a pointer to a reentrancy structure.

Returns
Return the converted substring value, if any. If no conversion could be performed, 0 is returned. If the correct value is out of the range of representable values, plus or minus HUGE_VAL is returned, and ERANGE is stored in errno. If the correct value would cause underflow, 0 is returned and ERANGE is stored in errno.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

2.41 `wcstol`—wide string to long

Synopsis

#include <wchar.h>
long wcstol(const wchar_t *__restrict s,
    wchar_t **__restrict ptr,int base);

long _wcstol_r(void *reent, 
    const wchar_t *s, wchar_t **ptr,int base);

Description
The function wcstol converts the wide string *s to a long. First, it breaks down the string into three parts: leading whitespace, which is ignored; a subject string consisting of characters resembling an integer in the radix specified by base; and a trailing portion consisting of zero or more unparseable characters, and always including the terminating null character. Then, it attempts to convert the subject string into a long and returns the result.

If the subject string is acceptable, and the value of base is zero, wcstol attempts to determine the radix from the input string. A string with a leading 0x is treated as a hexadecimal value; a string with a leading 0 and no x is treated as octal; all other strings are treated as decimal. If base is between 2 and 36, it is used as the conversion radix, as described above. If the subject string begins with a minus sign, the value is negated. Finally, a pointer to the first character past the converted subject string is stored in ptr, if ptr is not NULL.

If the subject string is empty (or not in acceptable form), no conversion is performed and the value of s is stored in ptr (if ptr is not NULL).

The alternate function _wcstol_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
wcstol returns the converted value, if any. If no conversion was made, 0 is returned.

wcstol returns LONG_MAX or LONG_MIN if the magnitude of the converted value is too large, and sets errno to ERANGE.

Portability
wcstol is ANSI.

No supporting OS subroutines are required.

2.42 `wcstoll`—wide string to long long

Synopsis

#include <wchar.h>
long long wcstoll(const wchar_t *__restrict s,
    wchar_t **__restrict ptr,int base);

long long _wcstoll_r(void *reent, 
    const wchar_t *s, wchar_t **ptr,int base);

Description
The function wcstoll converts the wide string *s to a long long. First, it breaks down the string into three parts: leading whitespace, which is ignored; a subject string consisting of characters resembling an integer in the radix specified by base; and a trailing portion consisting of zero or more unparseable characters, and always including the terminating null character. Then, it attempts to convert the subject string into a long long and returns the result.

If the subject string is acceptable, and the value of base is zero, wcstoll attempts to determine the radix from the input string. A string with a leading 0x is treated as a hexadecimal value; a string with a leading 0 and no x is treated as octal; all other strings are treated as decimal. If base is between 2 and 36, it is used as the conversion radix, as described above. If the subject string begins with a minus sign, the value is negated. Finally, a pointer to the first character past the converted subject string is stored in ptr, if ptr is not NULL.

If the subject string is empty (or not in acceptable form), no conversion is performed and the value of s is stored in ptr (if ptr is not NULL).

The alternate function _wcstoll_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
wcstoll returns the converted value, if any. If no conversion was made, 0 is returned.

wcstoll returns LONG_LONG_MAX or LONG_LONG_MIN if the magnitude of the converted value is too large, and sets errno to ERANGE.

Portability
wcstoll is ANSI.

No supporting OS subroutines are required.

2.43 `wcstoul`—wide string to unsigned long

Synopsis

#include <wchar.h>
unsigned long wcstoul(const wchar_t *__restrict s,
    wchar_t **__restrict ptr, int base);

unsigned long _wcstoul_r(void *reent, const wchar_t *s,
    wchar_t **ptr, int base);

Description
The function wcstoul converts the wide string *s to an unsigned long. First, it breaks down the string into three parts: leading whitespace, which is ignored; a subject string consisting of the digits meaningful in the radix specified by base (for example, 0 through 7 if the value of base is 8); and a trailing portion consisting of one or more unparseable characters, which always includes the terminating null character. Then, it attempts to convert the subject string into an unsigned long integer, and returns the result.

If the subject string is acceptable, and the value of base is zero, wcstoul attempts to determine the radix from the input string. A string with a leading 0x is treated as a hexadecimal value; a string with a leading 0 and no x is treated as octal; all other strings are treated as decimal. If base is between 2 and 36, it is used as the conversion radix, as described above. Finally, a pointer to the first character past the converted subject string is stored in ptr, if ptr is not NULL.

If the subject string is empty (that is, if *s does not start with a substring in acceptable form), no conversion is performed and the value of s is stored in ptr (if ptr is not NULL).

The alternate function _wcstoul_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
wcstoul returns the converted value, if any. If no conversion was made, 0 is returned.

wcstoul returns ULONG_MAX if the magnitude of the converted value is too large, and sets errno to ERANGE.

Portability
wcstoul is ANSI.

wcstoul requires no supporting OS subroutines.

2.44 `wcstoull`—wide string to unsigned long long

Synopsis

#include <wchar.h>
unsigned long long wcstoull(const wchar_t *__restrict s,
    wchar_t **__restrict ptr, int base);

unsigned long long _wcstoull_r(void *reent, const wchar_t *s,
    wchar_t **ptr, int base);

Description
The function wcstoull converts the wide string *s to an unsigned long long. First, it breaks down the string into three parts: leading whitespace, which is ignored; a subject string consisting of the digits meaningful in the radix specified by base (for example, 0 through 7 if the value of base is 8); and a trailing portion consisting of one or more unparseable characters, which always includes the terminating null character. Then, it attempts to convert the subject string into an unsigned long long integer, and returns the result.

If the value of base is zero, the subject string is expected to look like a normal C integer constant: an optional sign (+ or -), a possible 0x indicating hexadecimal radix or a possible <0> indicating octal radix, and a number. If base is between 2 and 36, the expected form of the subject is a sequence of digits (which may include letters, depending on the base) representing an integer in the radix specified by base. The letters a–z (or A–Z) are used as digits valued from 10 to 35. If base is 16, a leading 0x is permitted.

If the subject string is acceptable, and the value of base is zero, wcstoull attempts to determine the radix from the input string. A string with a leading 0x is treated as a hexadecimal value; a string with a leading 0 and no x is treated as octal; all other strings are treated as decimal. If base is between 2 and 36, it is used as the conversion radix, as described above. Finally, a pointer to the first character past the converted subject string is stored in ptr, if ptr is not NULL.

If the subject string is empty (that is, if *s does not start with a substring in acceptable form), no conversion is performed and the value of s is stored in ptr (if ptr is not NULL).

The alternate function _wcstoull_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
wcstoull returns 0 and sets errno to EINVAL if the value of base is not supported.

wcstoull returns the converted value, if any. If no conversion was made, 0 is returned.

wcstoull returns ULLONG_MAX if the magnitude of the converted value is too large, and sets errno to ERANGE.

Portability
wcstoull is ANSI.

wcstoull requires no supporting OS subroutines.

2.45 `system`—execute command string

Synopsis

#include <stdlib.h>
int system(char *s);

int _system_r(void *reent, char *s);

Description

Use system to pass a command string *s to /bin/sh on your system, and wait for it to finish executing.

Use “system(NULL)” to test whether your system has /bin/sh available.

The alternate function _system_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
system(NULL) returns a non-zero value if /bin/sh is available, and 0 if it is not.

With a command argument, the result of system is the exit status returned by /bin/sh.

Portability
ANSI C requires system, but leaves the nature and effects of a command processor undefined. ANSI C does, however, specify that system(NULL) return zero or nonzero to report on the existence of a command processor.

POSIX.2 requires system, and requires that it invoke a sh. Where sh is found is left unspecified.

Supporting OS subroutines required: _exit, _execve, _fork_r, _wait_r.

2.46 `wcstombs`—minimal wide char string to multibyte string converter

Synopsis

#include <stdlib.h>
size_t wcstombs(char *restrict s, const wchar_t *restrict pwc, size_t n);

Description
When _MB_CAPABLE is not defined, this is a minimal ANSI-conforming implementation of wcstombs. In this case, all wide-characters are expected to represent single bytes and so are converted simply by casting to char.

When _MB_CAPABLE is defined, this routine calls _wcstombs_r to perform the conversion, passing a state variable to allow state dependent decoding. The result is based on the locale setting which may be restricted to a defined set of locales.

Returns
This implementation of wcstombs returns 0 if s is NULL or is the empty string; it returns -1 if _MB_CAPABLE and one of the wide-char characters does not represent a valid multi-byte character; otherwise it returns the minimum of: n or the number of bytes that are transferred to s, not including the nul terminator.

If the return value is -1, the state of the pwc string is indeterminate. If the input has a length of 0, the output string will be modified to contain a wchar_t nul terminator if n > 0.

Portability
wcstombs is required in the ANSI C standard. However, the precise effects vary with the locale.

wcstombs requires no supporting OS subroutines.

2.47 `wctomb`—minimal wide char to multibyte converter

Synopsis

#include <stdlib.h>
int wctomb(char *s, wchar_t wchar);

Description
When _MB_CAPABLE is not defined, this is a minimal ANSI-conforming implementation of wctomb. The only “wide characters” recognized are single bytes, and they are “converted” to themselves.

When _MB_CAPABLE is defined, this routine calls _wctomb_r to perform the conversion, passing a state variable to allow state dependent decoding. The result is based on the locale setting which may be restricted to a defined set of locales.

Each call to wctomb modifies *s unless s is a null pointer or _MB_CAPABLE is defined and wchar is invalid.

Returns
This implementation of wctomb returns 0 if s is NULL; it returns -1 if _MB_CAPABLE is enabled and the wchar is not a valid multi-byte character, it returns 1 if _MB_CAPABLE is not defined or the wchar is in reality a single byte character, otherwise it returns the number of bytes in the multi-byte character.

Portability
wctomb is required in the ANSI C standard. However, the precise effects vary with the locale.

wctomb requires no supporting OS subroutines.

3 Character Type Macros and Functions (`ctype.h`)

This chapter groups macros (which are also available as subroutines) to classify characters into several categories (alphabetic, numeric, control characters, whitespace, and so on), or to perform simple character mappings.

The header file ctype.h defines the macros.

• isalnum:		Alphanumeric character predicate
• isalpha:		Alphabetic character predicate
• isascii:		ASCII character predicate
• iscntrl:		Control character predicate
• isdigit:		Decimal digit predicate
• islower:		Lowercase character predicate
• isprint:		Printable character predicates (isprint, isgraph)
• ispunct:		Punctuation character predicate
• isspace:		Whitespace character predicate
• isupper:		Uppercase character predicate
• isxdigit:		Hexadecimal digit predicate
• toascii:		Force integers to ASCII range
• tolower:		Translate characters to lowercase
• toupper:		Translate characters to uppercase
• iswalnum:		Alphanumeric wide character predicate
• iswalpha:		Alphabetic wide character predicate
• iswblank:		Blank wide character predicate
• iswcntrl:		Control wide character predicate
• iswdigit:		Decimal digit wide character predicate
• iswgraph:		Graphic wide character predicate
• iswlower:		Lowercase wide character predicate
• iswprint:		Printable wide character predicate
• iswpunct:		Punctuation wide character predicate
• iswspace:		Whitespace wide character predicate
• iswupper:		Uppercase wide character predicate
• iswxdigit:		Hexadecimal digit wide character predicate
• iswctype:		Extensible wide-character test
• wctype:		Compute wide-character test type
• towlower:		Translate wide characters to lowercase
• towupper:		Translate wide characters to uppercase
• towctrans:		Extensible wide-character translation
• wctrans:		Compute wide-character translation type

3.1 `isalnum`—alphanumeric character predicate

Synopsis

#include <ctype.h>
int isalnum(int c);

Description
isalnum is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for alphabetic or numeric ASCII characters, and 0 for other arguments. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef isalnum’.

Returns
isalnum returns non-zero if c is a letter (a–z or A–Z) or a digit (0–9).

Portability
isalnum is ANSI C.

No OS subroutines are required.

3.2 `isalpha`—alphabetic character predicate

Synopsis

#include <ctype.h>
int isalpha(int c);

Description
isalpha is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero when c represents an alphabetic ASCII character, and 0 otherwise. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef isalpha’.

Returns
isalpha returns non-zero if c is a letter (A–Z or a–z).

Portability
isalpha is ANSI C.

No supporting OS subroutines are required.

3.3 `isascii`—ASCII character predicate

Synopsis

#include <ctype.h>
int isascii(int c);

Description
isascii is a macro which returns non-zero when c is an ASCII character, and 0 otherwise. It is defined for all integer values.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef isascii’.

Returns
isascii returns non-zero if the low order byte of c is in the range 0 to 127 (0x00–0x7F).

Portability
isascii is ANSI C.

No supporting OS subroutines are required.

3.4 `iscntrl`—control character predicate

Synopsis

#include <ctype.h>
int iscntrl(int c);

Description
iscntrl is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for control characters, and 0 for other characters. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef iscntrl’.

Returns
iscntrl returns non-zero if c is a delete character or ordinary control character (0x7F or 0x00–0x1F).

Portability
iscntrl is ANSI C.

No supporting OS subroutines are required.

3.5 `isdigit`—decimal digit predicate

Synopsis

#include <ctype.h>
int isdigit(int c);

Description
isdigit is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for decimal digits, and 0 for other characters. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef isdigit’.

Returns
isdigit returns non-zero if c is a decimal digit (0–9).

Portability
isdigit is ANSI C.

No supporting OS subroutines are required.

3.6 `islower`—lowercase character predicate

Synopsis

#include <ctype.h>
int islower(int c);

Description
islower is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for minuscules (lowercase alphabetic characters), and 0 for other characters. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef islower’.

Returns
islower returns non-zero if c is a lowercase letter (a–z).

Portability
islower is ANSI C.

No supporting OS subroutines are required.

3.7 `isprint`, `isgraph`—printable character predicates

Synopsis

#include <ctype.h>
int isprint(int c);
int isgraph(int c);

Description
isprint is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for printable characters, and 0 for other character arguments. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining either macro using ‘#undef isprint’ or ‘#undef isgraph’.

Returns
isprint returns non-zero if c is a printing character, (0x20–0x7E). isgraph behaves identically to isprint, except that the space character (0x20) is excluded.

Portability
isprint and isgraph are ANSI C.

No supporting OS subroutines are required.

3.8 `ispunct`—punctuation character predicate

Synopsis

#include <ctype.h>
int ispunct(int c);

Description
ispunct is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for printable punctuation characters, and 0 for other characters. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef ispunct’.

Returns
ispunct returns non-zero if c is a printable punctuation character (isgraph(c) && !isalnum(c)).

Portability
ispunct is ANSI C.

No supporting OS subroutines are required.

3.9 `isspace`—whitespace character predicate

Synopsis

#include <ctype.h>
int isspace(int c);

Description
isspace is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for whitespace characters, and 0 for other characters. It is defined only when isascii(c) is true or c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef isspace’.

Returns
isspace returns non-zero if c is a space, tab, carriage return, new line, vertical tab, or formfeed (0x09–0x0D, 0x20).

Portability
isspace is ANSI C.

No supporting OS subroutines are required.

3.10 `isupper`—uppercase character predicate

Synopsis

#include <ctype.h>
int isupper(int c);

Description
isupper is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for uppercase letters (A–Z), and 0 for other characters. It is defined only when isascii(c) is true or c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef isupper’.

Returns
isupper returns non-zero if c is a uppercase letter (A-Z).

Portability
isupper is ANSI C.

No supporting OS subroutines are required.

3.11 `isxdigit`—hexadecimal digit predicate

Synopsis

#include <ctype.h>
int isxdigit(int c);

Description
isxdigit is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for hexadecimal digits, and 0 for other characters. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef isxdigit’.

Returns
isxdigit returns non-zero if c is a hexadecimal digit (0–9, a–f, or A–F).

Portability
isxdigit is ANSI C.

No supporting OS subroutines are required.

3.12 `toascii`—force integers to ASCII range

Synopsis

#include <ctype.h>
int toascii(int c);

Description
toascii is a macro which coerces integers to the ASCII range (0–127) by zeroing any higher-order bits.

You can use a compiled subroutine instead of the macro definition by undefining this macro using ‘#undef toascii’.

Returns
toascii returns integers between 0 and 127.

Portability
toascii is not ANSI C.

No supporting OS subroutines are required.

3.13 `tolower`—translate characters to lowercase

Synopsis

#include <ctype.h>
int tolower(int c);
int _tolower(int c);

Description
tolower is a macro which converts uppercase characters to lowercase, leaving all other characters unchanged. It is only defined when c is an integer in the range EOF to 255.

You can use a compiled subroutine instead of the macro definition by undefining this macro using ‘#undef tolower’.

_tolower performs the same conversion as tolower, but should only be used when c is known to be an uppercase character (A–Z).

Returns
tolower returns the lowercase equivalent of c when it is a character between A and Z, and c otherwise.

_tolower returns the lowercase equivalent of c when it is a character between A and Z. If c is not one of these characters, the behaviour of _tolower is undefined.

Portability
tolower is ANSI C. _tolower is not recommended for portable programs.

No supporting OS subroutines are required.

3.14 `toupper`—translate characters to uppercase

Synopsis

#include <ctype.h>
int toupper(int c);
int _toupper(int c);

Description
toupper is a macro which converts lowercase characters to uppercase, leaving all other characters unchanged. It is only defined when c is an integer in the range EOF to 255.

You can use a compiled subroutine instead of the macro definition by undefining this macro using ‘#undef toupper’.

_toupper performs the same conversion as toupper, but should only be used when c is known to be a lowercase character (a–z).

Returns
toupper returns the uppercase equivalent of c when it is a character between a and z, and c otherwise.

_toupper returns the uppercase equivalent of c when it is a character between a and z. If c is not one of these characters, the behaviour of _toupper is undefined.

Portability
toupper is ANSI C. _toupper is not recommended for portable programs.

No supporting OS subroutines are required.

3.15 `iswalnum`—alphanumeric wide character test

Synopsis

#include <wctype.h>
int iswalnum(wint_t c);

Description
iswalnum is a function which classifies wide-character values that are alphanumeric.

Returns
iswalnum returns non-zero if c is a alphanumeric wide character.

Portability
iswalnum is C99.

No supporting OS subroutines are required.

3.16 `iswalpha`—alphabetic wide character test

Synopsis

#include <wctype.h>
int iswalpha(wint_t c);

Description
iswalpha is a function which classifies wide-character values that are alphabetic.

Returns
iswalpha returns non-zero if c is an alphabetic wide character.

Portability
iswalpha is C99.

No supporting OS subroutines are required.

3.17 `iswcntrl`—control wide character test

Synopsis

#include <wctype.h>
int iswcntrl(wint_t c);

Description
iswcntrl is a function which classifies wide-character values that are categorized as control characters.

Returns
iswcntrl returns non-zero if c is a control wide character.

Portability
iswcntrl is C99.

No supporting OS subroutines are required.

3.18 `iswblank`—blank wide character test

Synopsis

#include <wctype.h>
int iswblank(wint_t c);

Description
iswblank is a function which classifies wide-character values that are categorized as blank.

Returns
iswblank returns non-zero if c is a blank wide character.

Portability
iswblank is C99.

No supporting OS subroutines are required.

3.19 `iswdigit`—decimal digit wide character test

Synopsis

#include <wctype.h>
int iswdigit(wint_t c);

Description
iswdigit is a function which classifies wide-character values that are decimal digits.

Returns
iswdigit returns non-zero if c is a decimal digit wide character.

Portability
iswdigit is C99.

No supporting OS subroutines are required.

3.20 `iswgraph`—graphic wide character test

Synopsis

#include <wctype.h>
int iswgraph(wint_t c);

Description
iswgraph is a function which classifies wide-character values that are graphic.

Returns
iswgraph returns non-zero if c is a graphic wide character.

Portability
iswgraph is C99.

No supporting OS subroutines are required.

3.21 `iswlower`—lowercase wide character test

Synopsis

#include <wctype.h>
int iswlower(wint_t c);

Description
iswlower is a function which classifies wide-character values that have uppercase translations.

Returns
iswlower returns non-zero if c is a lowercase wide character.

Portability
iswlower is C99.

No supporting OS subroutines are required.

3.22 `iswprint`—printable wide character test

Synopsis

#include <wctype.h>
int iswprint(wint_t c);

Description
iswprint is a function which classifies wide-character values that are printable.

Returns
iswprint returns non-zero if c is a printable wide character.

Portability
iswprint is C99.

No supporting OS subroutines are required.

3.23 `iswpunct`—punctuation wide character test

Synopsis

#include <wctype.h>
int iswpunct(wint_t c);

Description
iswpunct is a function which classifies wide-character values that are punctuation.

Returns
iswpunct returns non-zero if c is a punctuation wide character.

Portability
iswpunct is C99.

No supporting OS subroutines are required.

3.24 `iswspace`—whitespace wide character test

Synopsis

#include <wctype.h>
int iswspace(wint_t c);

Description
iswspace is a function which classifies wide-character values that are categorized as whitespace.

Returns
iswspace returns non-zero if c is a whitespace wide character.

Portability
iswspace is C99.

No supporting OS subroutines are required.

3.25 `iswupper`—uppercase wide character test

Synopsis

#include <wctype.h>
int iswupper(wint_t c);

Description
iswupper is a function which classifies wide-character values that have uppercase translations.

Returns
iswupper returns non-zero if c is a uppercase wide character.

Portability
iswupper is C99.

No supporting OS subroutines are required.

3.26 `iswxdigit`—hexadecimal digit wide character test

Synopsis

#include <wctype.h>
int iswxdigit(wint_t c);

Description
iswxdigit is a function which classifies wide character values that are hexadecimal digits.

Returns
iswxdigit returns non-zero if c is a hexadecimal digit wide character.

Portability
iswxdigit is C99.

No supporting OS subroutines are required.

3.27 `iswctype`—extensible wide-character test

Synopsis

#include <wctype.h>
int iswctype(wint_t c, wctype_t desc);

Description
iswctype is a function which classifies wide-character values using the wide-character test specified by desc.

Returns
iswctype returns non-zero if and only if c matches the test specified by desc. If desc is unknown, zero is returned.

Portability
iswctype is C99.

No supporting OS subroutines are required.

3.28 `wctype`—get wide-character classification type

Synopsis

#include <wctype.h>
wctype_t wctype(const char *c);

Description
wctype is a function which takes a string c and gives back the appropriate wctype_t type value associated with the string, if one exists. The following values are guaranteed to be recognized: "alnum", "alpha", "blank", "cntrl", "digit", "graph", "lower", "print", "punct", "space", "upper", and "xdigit".

Returns
wctype returns 0 and sets errno to EINVAL if the given name is invalid. Otherwise, it returns a valid non-zero wctype_t value.

Portability
wctype is C99.

No supporting OS subroutines are required.

3.29 `towlower`—translate wide characters to lowercase

Synopsis

#include <wctype.h>
wint_t towlower(wint_t c);

Description
towlower is a function which converts uppercase wide characters to lowercase, leaving all other characters unchanged.

Returns
towlower returns the lowercase equivalent of c when it is a uppercase wide character; otherwise, it returns the input character.

Portability
towlower is C99.

No supporting OS subroutines are required.

3.30 `towupper`—translate wide characters to uppercase

Synopsis

#include <wctype.h>
wint_t towupper(wint_t c);

Description
towupper is a function which converts lowercase wide characters to uppercase, leaving all other characters unchanged.

Returns
towupper returns the uppercase equivalent of c when it is a lowercase wide character, otherwise, it returns the input character.

Portability
towupper is C99.

No supporting OS subroutines are required.

3.31 `towctrans`—extensible wide-character translation

Synopsis

#include <wctype.h>
wint_t towctrans(wint_t c, wctrans_t w);

Description
towctrans is a function which converts wide characters based on a specified translation type w. If the translation type is invalid or cannot be applied to the current character, no change to the character is made.

Returns
towctrans returns the translated equivalent of c when it is a valid for the given translation, otherwise, it returns the input character. When the translation type is invalid, errno is set EINVAL.

Portability
towctrans is C99.

No supporting OS subroutines are required.

3.32 `wctrans`—get wide-character translation type

Synopsis

#include <wctype.h>
wctrans_t wctrans(const char *c);

Description
wctrans is a function which takes a string c and gives back the appropriate wctrans_t type value associated with the string, if one exists. The following values are guaranteed to be recognized: "tolower" and "toupper".

Returns
wctrans returns 0 and sets errno to EINVAL if the given name is invalid. Otherwise, it returns a valid non-zero wctrans_t value.

Portability
wctrans is C99.

No supporting OS subroutines are required.

4 Input and Output (`stdio.h`)

This chapter comprises functions to manage files or other input/output streams. Among these functions are subroutines to generate or scan strings according to specifications from a format string.

The underlying facilities for input and output depend on the host system, but these functions provide a uniform interface.

The corresponding declarations are in stdio.h.

The reentrant versions of these functions use macros

_stdin_r(reent)
_stdout_r(reent)
_stderr_r(reent)

instead of the globals stdin, stdout, and stderr. The argument <[reent]> is a pointer to a reentrancy structure.

• clearerr:		Clear file or stream error indicator
• diprintf:		Print to a file descriptor (integer only)
• dprintf:		Print to a file descriptor
• fclose:		Close a file
• fcloseall:		Close all files
• fdopen:		Turn an open file into a stream
• feof:		Test for end of file
• ferror:		Test whether read/write error has occurred
• fflush:		Flush buffered file output
• fgetc:		Get a character from a file or stream
• fgetpos:		Record position in a stream or file
• fgets:		Get character string from a file or stream
• fgetwc:		Get a wide character from a file or stream
• fgetws:		Get a wide character string from a file or stream
• fileno:		Get file descriptor associated with stream
• fmemopen:		Open a stream around a fixed-length buffer
• fopen:		Open a file
• fopencookie:		Open a stream with custom callbacks
• fpurge:		Discard all pending I/O on a stream
• fputc:		Write a character on a stream or file
• fputs:		Write a character string in a file or stream
• fputwc:		Write a wide character to a file or stream
• fputws:		Write a wide character string to a file or stream
• fread:		Read array elements from a file
• freopen:		Open a file using an existing file descriptor
• fseek:		Set file position
• __fsetlocking:		Set or query locking mode on FILE stream
• fsetpos:		Restore position of a stream or file
• ftell:		Return position in a stream or file
• funopen:		Open a stream with custom callbacks
• fwide:		Set and determine the orientation of a FILE stream
• fwrite:		Write array elements from memory to a file or stream
• getc:		Get a character from a file or stream (macro)
• getc_unlocked:		Get a character from a file or stream (macro)
• getchar:		Get a character from standard input (macro)
• getchar_unlocked:		Get a character from standard input (macro)
• getdelim:		Get character string from a file or stream
• getline:		Get character string from a file or stream
• gets:		Get character string from standard input (obsolete)
• getw:		Get a word (int) from a file or stream
• getwchar:		Get a wide character from standard input
• mktemp:		Generate unused file name
• open_memstream:		Open a write stream around an arbitrary-length buffer
• perror:		Print an error message on standard error
• putc:		Write a character on a stream or file (macro)
• putc_unlocked:		Write a character on a stream or file (macro)
• putchar:		Write a character on standard output (macro)
• putchar_unlocked:		Write a character on standard output (macro)
• puts:		Write a character string on standard output
• putw:		Write a word (int) to a file or stream
• putwchar:		Write a wide character to standard output
• remove:		Delete a file’s name
• rename:		Rename a file
• rewind:		Reinitialize a file or stream
• setbuf:		Specify full buffering for a file or stream
• setbuffer:		Specify full buffering for a file or stream with size
• setlinebuf:		Specify line buffering for a file or stream
• setvbuf:		Specify buffering for a file or stream
• siprintf:		Write formatted output (integer only)
• siscanf:		Scan and format input (integer only)
• sprintf:		Write formatted output
• sscanf:		Scan and format input
• stdio_ext:		Access internals of FILE structure
• swprintf:		Write formatted wide character output
• swscanf:		Scan and format wide character input
• tmpfile:		Create a temporary file
• tmpnam:		Generate name for a temporary file
• ungetc:		Push data back into a stream
• ungetwc:		Push wide character data back into a stream
• vfprintf:		Format variable argument list
• vfscanf:		Scan variable argument list
• vfwprintf:		Format variable wide character argument list
• vfwscanf:		Scan and format argument list from wide character input
• viprintf:		Format variable argument list (integer only)
• viscanf:		Scan variable format list (integer only)

4.1 `clearerr`, `clearerr_unlocked`—clear file or stream error indicator

Synopsis

#include <stdio.h>
void clearerr(FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
void clearerr_unlocked(FILE *fp);

Description
The stdio functions maintain an error indicator with each file pointer fp, to record whether any read or write errors have occurred on the associated file or stream. Similarly, it maintains an end-of-file indicator to record whether there is no more data in the file.

Use clearerr to reset both of these indicators.

See ferror and feof to query the two indicators.

clearerr_unlocked is a non-thread-safe version of clearerr. clearerr_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then clearerr_unlocked is equivalent to clearerr.

Returns
clearerr does not return a result.

Portability
ANSI C requires clearerr.

clearerr_unlocked is a BSD extension also provided by GNU libc.

No supporting OS subroutines are required.

4.2 `diprintf`, `vdiprintf`—print to a file descriptor (integer only)

Synopsis

#include <stdio.h>
#include <stdarg.h>
int diprintf(int fd, const char *format, ...);
int vdiprintf(int fd, const char *format, va_list ap);
int _diprintf_r(struct _reent *ptr, int fd,
    const char *format, ...);
int _vdiprintf_r(struct _reent *ptr, int fd,
    const char *format, va_list ap);

Description
diprintf and vdiprintf are similar to dprintf and vdprintf, except that only integer format specifiers are processed.

The functions _diprintf_r and _vdiprintf_r are simply reentrant versions of the functions above.

Returns
Similar to dprintf and vdprintf.

Portability
This set of functions is an integer-only extension, and is not portable.

Supporting OS subroutines required: sbrk, write.

4.3 `dprintf`, `vdprintf`—print to a file descriptor

Synopsis

#include <stdio.h>
#include <stdarg.h>
int dprintf(int fd, const char *restrict format, ...);
int vdprintf(int fd, const char *restrict format,
    va_list ap);
int _dprintf_r(struct _reent *ptr, int fd,
    const char *restrict format, ...);
int _vdprintf_r(struct _reent *ptr, int fd,
    const char *restrict format, va_list ap);

Description
dprintf and vdprintf allow printing a format, similarly to printf, but write to a file descriptor instead of to a FILE stream.

The functions _dprintf_r and _vdprintf_r are simply reentrant versions of the functions above.

Returns
The return value and errors are exactly as for write, except that errno may also be set to ENOMEM if the heap is exhausted.

Portability
This function is originally a GNU extension in glibc and is not portable.

Supporting OS subroutines required: sbrk, write.

4.4 `fclose`—close a file

Synopsis

#include <stdio.h>
int fclose(FILE *fp);
int _fclose_r(struct _reent *reent, FILE *fp);

Description
If the file or stream identified by fp is open, fclose closes it, after first ensuring that any pending data is written (by calling fflush(fp)).

The alternate function _fclose_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
fclose returns 0 if successful (including when fp is NULL or not an open file); otherwise, it returns EOF.

Portability
fclose is required by ANSI C.

Required OS subroutines: close, fstat, isatty, lseek, read, sbrk, write.

4.5 `fcloseall`—close all files

Synopsis

#include <stdio.h>
int fcloseall(void);
int _fcloseall_r (struct _reent *ptr);

Description
fcloseall closes all files in the current reentrancy struct’s domain. The function _fcloseall_r is the same function, except the reentrancy struct is passed in as the ptr argument.

This function is not recommended as it closes all streams, including the std streams.

Returns
fclose returns 0 if all closes are successful. Otherwise, EOF is returned.

Portability
fcloseall is a glibc extension.

Required OS subroutines: close, fstat, isatty, lseek, read, sbrk, write.

4.6 `fdopen`—turn open file into a stream

Synopsis

#include <stdio.h>
FILE *fdopen(int fd, const char *mode);
FILE *_fdopen_r(struct _reent *reent,
    int fd, const char *mode);

Description
fdopen produces a file descriptor of type FILE *, from a descriptor for an already-open file (returned, for example, by the system subroutine open rather than by fopen). The mode argument has the same meanings as in fopen.

Returns
File pointer or NULL, as for fopen.

Portability
fdopen is ANSI.

4.7 `feof`, `feof_unlocked`—test for end of file

Synopsis

#include <stdio.h>
int feof(FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
int feof_unlocked(FILE *fp);

Description
feof tests whether or not the end of the file identified by fp has been reached.

feof_unlocked is a non-thread-safe version of feof. feof_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then feof_unlocked is equivalent to feof.

Returns
feof returns 0 if the end of file has not yet been reached; if at end of file, the result is nonzero.

Portability
feof is required by ANSI C.

feof_unlocked is a BSD extension also provided by GNU libc.

No supporting OS subroutines are required.

4.8 `ferror`, `ferror_unlocked`—test whether read/write error has occurred

Synopsis

#include <stdio.h>
int ferror(FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
int ferror_unlocked(FILE *fp);

See clearerr to reset the error indicator.

ferror_unlocked is a non-thread-safe version of ferror. ferror_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then ferror_unlocked is equivalent to ferror.

Returns
ferror returns 0 if no errors have occurred; it returns a nonzero value otherwise.

Portability
ANSI C requires ferror.

ferror_unlocked is a BSD extension also provided by GNU libc.

No supporting OS subroutines are required.

4.9 `fflush`, `fflush_unlocked`—flush buffered file output

Synopsis

#include <stdio.h>
int fflush(FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
int fflush_unlocked(FILE *fp);

#include <stdio.h>
int _fflush_r(struct _reent *reent, FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
int _fflush_unlocked_r(struct _reent *reent, FILE *fp);

Description
The stdio output functions can buffer output before delivering it to the host system, in order to minimize the overhead of system calls.

Use fflush to deliver any such pending output (for the file or stream identified by fp) to the host system.

If fp is NULL, fflush delivers pending output from all open files.

Additionally, if fp is a seekable input stream visiting a file descriptor, set the position of the file descriptor to match next unread byte, useful for obeying POSIX semantics when ending a process without consuming all input from the stream.

fflush_unlocked is a non-thread-safe version of fflush. fflush_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fflush_unlocked is equivalent to fflush.

The alternate functions _fflush_r and _fflush_unlocked_r are reentrant versions, where the extra argument reent is a pointer to a reentrancy structure, and fp must not be NULL.

Returns
fflush returns 0 unless it encounters a write error; in that situation, it returns EOF.

Portability
ANSI C requires fflush. The behavior on input streams is only specified by POSIX, and not all implementations follow POSIX rules.

fflush_unlocked is a BSD extension also provided by GNU libc.

No supporting OS subroutines are required.

4.10 `fgetc`, `fgetc_unlocked`—get a character from a file or stream

Synopsis

#include <stdio.h>
int fgetc(FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
int fgetc_unlocked(FILE *fp);

#include <stdio.h>
int _fgetc_r(struct _reent *ptr, FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
int _fgetc_unlocked_r(struct _reent *ptr, FILE *fp);

Description
Use fgetc to get the next single character from the file or stream identified by fp. As a side effect, fgetc advances the file’s current position indicator.

For a macro version of this function, see getc.

fgetc_unlocked is a non-thread-safe version of fgetc. fgetc_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fgetc_unlocked is equivalent to fgetc.

The functions _fgetc_r and _fgetc_unlocked_r are simply reentrant versions that are passed the additional reentrant structure pointer argument: ptr.

Returns
The next character (read as an unsigned char, and cast to int), unless there is no more data, or the host system reports a read error; in either of these situations, fgetc returns EOF.

You can distinguish the two situations that cause an EOF result by using the ferror and feof functions.

Portability
ANSI C requires fgetc.

fgetc_unlocked is a BSD extension also provided by GNU libc.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.11 `fgetpos`—record position in a stream or file

Synopsis

#include <stdio.h>
int fgetpos(FILE *restrict fp, fpos_t *restrict pos);
int _fgetpos_r(struct _reent *ptr, FILE *restrict fp, fpos_t *restrict pos);

Description
Objects of type FILE can have a “position” that records how much of the file your program has already read. Many of the stdio functions depend on this position, and many change it as a side effect.

You can use fgetpos to report on the current position for a file identified by fp; fgetpos will write a value representing that position at *pos. Later, you can use this value with fsetpos to return the file to this position.

In the current implementation, fgetpos simply uses a character count to represent the file position; this is the same number that would be returned by ftell.

Returns
fgetpos returns 0 when successful. If fgetpos fails, the result is 1. Failure occurs on streams that do not support positioning; the global errno indicates this condition with the value ESPIPE.

Portability
fgetpos is required by the ANSI C standard, but the meaning of the value it records is not specified beyond requiring that it be acceptable as an argument to fsetpos. In particular, other conforming C implementations may return a different result from ftell than what fgetpos writes at *pos.

No supporting OS subroutines are required.

4.12 `fgets`, `fgets_unlocked`—get character string from a file or stream

Synopsis

#include <stdio.h>
char *fgets(char *restrict buf, int n, FILE *restrict fp);

#define _GNU_SOURCE
#include <stdio.h>
char *fgets_unlocked(char *restrict buf, int n, FILE *restrict fp);

#include <stdio.h>
char *_fgets_r(struct _reent *ptr, char *restrict buf, int n, FILE *restrict fp);

#include <stdio.h>
char *_fgets_unlocked_r(struct _reent *ptr, char *restrict buf, int n, FILE *restrict fp);

Description
Reads at most n-1 characters from fp until a newline is found. The characters including to the newline are stored in buf. The buffer is terminated with a 0.

fgets_unlocked is a non-thread-safe version of fgets. fgets_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fgets_unlocked is equivalent to fgets.

The functions _fgets_r and _fgets_unlocked_r are simply reentrant versions that are passed the additional reentrant structure pointer argument: ptr.

Returns
fgets returns the buffer passed to it, with the data filled in. If end of file occurs with some data already accumulated, the data is returned with no other indication. If no data are read, NULL is returned instead.

Portability
fgets should replace all uses of gets. Note however that fgets returns all of the data, while gets removes the trailing newline (with no indication that it has done so.)

fgets_unlocked is a GNU extension.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.13 `fgetwc`, `getwc`, `fgetwc_unlocked`, `getwc_unlocked`—get a wide character from a file or stream

Synopsis

#include <stdio.h>
#include <wchar.h>
wint_t fgetwc(FILE *fp);

#define _GNU_SOURCE
#include <stdio.h>
#include <wchar.h>
wint_t fgetwc_unlocked(FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t _fgetwc_r(struct _reent *ptr, FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t _fgetwc_unlocked_r(struct _reent *ptr, FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t getwc(FILE *fp);

#define _GNU_SOURCE
#include <stdio.h>
#include <wchar.h>
wint_t getwc_unlocked(FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t _getwc_r(struct _reent *ptr, FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t _getwc_unlocked_r(struct _reent *ptr, FILE *fp);

Description
Use fgetwc to get the next wide character from the file or stream identified by fp. As a side effect, fgetwc advances the file’s current position indicator.

fgetwc_unlocked is a non-thread-safe version of fgetwc. fgetwc_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fgetwc_unlocked is equivalent to fgetwc.

The getwc and getwc_unlocked functions or macros functions identically to fgetwc and fgetwc_unlocked. It may be implemented as a macro, and may evaluate its argument more than once. There is no reason ever to use it.

_fgetwc_r, _getwc_r, _fgetwc_unlocked_r, and _getwc_unlocked_r are simply reentrant versions of the above functions that are passed the additional reentrant structure pointer argument: ptr.

Returns
The next wide character cast to wint_t), unless there is no more data, or the host system reports a read error; in either of these situations, fgetwc and getwc return WEOF.

You can distinguish the two situations that cause an EOF result by using the ferror and feof functions.

Portability
fgetwc and getwc are required by C99 and POSIX.1-2001.

fgetwc_unlocked and getwc_unlocked are GNU extensions.

4.14 `fgetws`, `fgetws_unlocked`—get wide character string from a file or stream

Synopsis

#include <wchar.h>
wchar_t *fgetws(wchar_t *__restrict ws, int n,
    FILE *__restrict fp);

#define _GNU_SOURCE
#include <wchar.h>
wchar_t *fgetws_unlocked(wchar_t *__restrict ws, int n,
    FILE *__restrict fp);

#include <wchar.h>
wchar_t *_fgetws_r(struct _reent *ptr, wchar_t *ws,
    int n, FILE *fp);

#include <wchar.h>
wchar_t *_fgetws_unlocked_r(struct _reent *ptr, wchar_t *ws,
    int n, FILE *fp);

Description
Reads at most n-1 wide characters from fp until a newline is found. The wide characters including to the newline are stored in ws. The buffer is terminated with a 0.

fgetws_unlocked is a non-thread-safe version of fgetws. fgetws_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fgetws_unlocked is equivalent to fgetws.

The _fgetws_r and _fgetws_unlocked_r functions are simply reentrant version of the above and are passed an additional reentrancy structure pointer: ptr.

Returns
fgetws returns the buffer passed to it, with the data filled in. If end of file occurs with some data already accumulated, the data is returned with no other indication. If no data are read, NULL is returned instead.

Portability
fgetws is required by C99 and POSIX.1-2001.

fgetws_unlocked is a GNU extension.

4.15 `fileno`, `fileno_unlocked`—return file descriptor associated with stream

Synopsis

#include <stdio.h>
int fileno(FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
int fileno_unlocked(FILE *fp);

Description
You can use fileno to return the file descriptor identified by fp.

fileno_unlocked is a non-thread-safe version of fileno. fileno_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fileno_unlocked is equivalent to fileno.

Returns
fileno returns a non-negative integer when successful. If fp is not an open stream, fileno returns -1.

Portability
fileno is not part of ANSI C. POSIX requires fileno.

fileno_unlocked is a BSD extension also provided by GNU libc.

Supporting OS subroutines required: none.

4.16 `fmemopen`—open a stream around a fixed-length string

Synopsis

#include <stdio.h>
FILE *fmemopen(void *restrict buf, size_t size,
    const char *restrict mode);

Description
fmemopen creates a seekable FILE stream that wraps a fixed-length buffer of size bytes starting at buf. The stream is opened with mode treated as in fopen, where append mode starts writing at the first NUL byte. If buf is NULL, then size bytes are automatically provided as if by malloc, with the initial size of 0, and mode must contain + so that data can be read after it is written.

The stream maintains a current position, which moves according to bytes read or written, and which can be one past the end of the array. The stream also maintains a current file size, which is never greater than size. If mode starts with r, the position starts at 0, and file size starts at size if buf was provided. If mode starts with w, the position and file size start at 0, and if buf was provided, the first byte is set to NUL. If mode starts with a, the position and file size start at the location of the first NUL byte, or else size if buf was provided.

When reading, NUL bytes have no significance, and reads cannot exceed the current file size. When writing, the file size can increase up to size as needed, and NUL bytes may be embedded in the stream (see open_memstream for an alternative that automatically enlarges the buffer). When the stream is flushed or closed after a write that changed the file size, a NUL byte is written at the current position if there is still room; if the stream is not also open for reading, a NUL byte is additionally written at the last byte of buf when the stream has exceeded size, so that a write-only buf is always NUL-terminated when the stream is flushed or closed (and the initial size should take this into account). It is not possible to seek outside the bounds of size. A NUL byte written during a flush is restored to its previous value when seeking elsewhere in the string.

Returns
The return value is an open FILE pointer on success. On error, NULL is returned, and errno will be set to EINVAL if size is zero or mode is invalid, ENOMEM if buf was NULL and memory could not be allocated, or EMFILE if too many streams are already open.

Portability
This function is being added to POSIX 200x, but is not in POSIX 2001.

Supporting OS subroutines required: sbrk.

4.17 `fopen`—open a file

Synopsis

#include <stdio.h>
FILE *fopen(const char *file, const char *mode);

FILE *_fopen_r(struct _reent *reent, 
    const char *file, const char *mode);

Description
fopen initializes the data structures needed to read or write a file. Specify the file’s name as the string at file, and the kind of access you need to the file with the string at mode.

The alternate function _fopen_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Three fundamental kinds of access are available: read, write, and append. *mode must begin with one of the three characters ‘r’, ‘w’, or ‘a’, to select one of these:

r: Open the file for reading; the operation will fail if the file does not exist, or if the host system does not permit you to read it.
w: Open the file for writing from the beginning of the file: effectively, this always creates a new file. If the file whose name you specified already existed, its old contents are discarded.
a: Open the file for appending data, that is writing from the end of file. When you open a file this way, all data always goes to the current end of file; you cannot change this using fseek.

Some host systems distinguish between “binary” and “text” files. Such systems may perform data transformations on data written to, or read from, files opened as “text”. If your system is one of these, then you can append a ‘b’ to any of the three modes above, to specify that you are opening the file as a binary file (the default is to open the file as a text file).

‘rb’, then, means “read binary”; ‘wb’, “write binary”; and ‘ab’, “append binary”.

To make C programs more portable, the ‘b’ is accepted on all systems, whether or not it makes a difference.

Finally, you might need to both read and write from the same file. You can also append a ‘+’ to any of the three modes, to permit this. (If you want to append both ‘b’ and ‘+’, you can do it in either order: for example, "rb+" means the same thing as "r+b" when used as a mode string.)

Use "r+" (or "rb+") to permit reading and writing anywhere in an existing file, without discarding any data; "w+" (or "wb+") to create a new file (or begin by discarding all data from an old one) that permits reading and writing anywhere in it; and "a+" (or "ab+") to permit reading anywhere in an existing file, but writing only at the end.

Returns
fopen returns a file pointer which you can use for other file operations, unless the file you requested could not be opened; in that situation, the result is NULL. If the reason for failure was an invalid string at mode, errno is set to EINVAL.

Portability
fopen is required by ANSI C.

Supporting OS subroutines required: close, fstat, isatty, lseek, open, read, sbrk, write.

4.18 `fopencookie`—open a stream with custom callbacks

Synopsis

#include <stdio.h>
FILE *fopencookie(const void *cookie, const char *mode,
    cookie_io_functions_t functions);

Description
fopencookie creates a FILE stream where I/O is performed using custom callbacks. The callbacks are registered via the structure:

typedef ssize_t (*cookie_read_function_t)(void *_cookie, char *_buf, size_t _n); typedef ssize_t (*cookie_write_function_t)(void *_cookie, const char *_buf, size_t _n); typedef int (*cookie_seek_function_t)(void *_cookie, off_t *_off, int _whence); typedef int (*cookie_close_function_t)(void *_cookie);

	typedef struct
	{
		cookie_read_function_t	*read;
		cookie_write_function_t *write;
		cookie_seek_function_t	*seek;
		cookie_close_function_t *close;
	} cookie_io_functions_t;

The stream is opened with mode treated as in fopen. The callbacks functions.read and functions.write may only be NULL when mode does not require them.

functions.read should return -1 on failure, or else the number of bytes read (0 on EOF). It is similar to read, except that cookie will be passed as the first argument.

functions.write should return -1 on failure, or else the number of bytes written. It is similar to write, except that cookie will be passed as the first argument.

functions.seek should return -1 on failure, and 0 on success, with _off set to the current file position. It is a cross between lseek and fseek, with the _whence argument interpreted in the same manner. A NULL functions.seek makes the stream behave similarly to a pipe in relation to stdio functions that require positioning.

functions.close should return -1 on failure, or 0 on success. It is similar to close, except that cookie will be passed as the first argument. A NULL functions.close merely flushes all data then lets fclose succeed. A failed close will still invalidate the stream.

Read and write I/O functions are allowed to change the underlying buffer on fully buffered or line buffered streams by calling setvbuf. They are also not required to completely fill or empty the buffer. They are not, however, allowed to change streams from unbuffered to buffered or to change the state of the line buffering flag. They must also be prepared to have read or write calls occur on buffers other than the one most recently specified.

Returns
The return value is an open FILE pointer on success. On error, NULL is returned, and errno will be set to EINVAL if a function pointer is missing or mode is invalid, ENOMEM if the stream cannot be created, or EMFILE if too many streams are already open.

Portability
This function is a newlib extension, copying the prototype from Linux. It is not portable. See also the funopen interface from BSD.

Supporting OS subroutines required: sbrk.

4.19 `fpurge`—discard pending file I/O

Synopsis

#include <stdio.h>
int fpurge(FILE *fp);

int _fpurge_r(struct _reent *reent, FILE *fp);

#include <stdio.h>
#include <stdio_ext.h>
void  __fpurge(FILE *fp);

Description
Use fpurge to clear all buffers of the given stream. For output streams, this discards data not yet written to disk. For input streams, this discards any data from ungetc and any data retrieved from disk but not yet read via getc. This is more severe than fflush, and generally is only needed when manually altering the underlying file descriptor of a stream.

__fpurge behaves exactly like fpurge but does not return a value.

The alternate function _fpurge_r is a reentrant version, where the extra argument reent is a pointer to a reentrancy structure, and fp must not be NULL.

Returns
fpurge returns 0 unless fp is not valid, in which case it returns EOF and sets errno.

Portability
These functions are not portable to any standard.

No supporting OS subroutines are required.

4.20 `fputc`, `fputc_unlocked`—write a character on a stream or file

Synopsis

#include <stdio.h>
int fputc(int ch, FILE *fp);

#define _BSD_SOURCE
#include <stdio.h>
int fputc_unlocked(int ch, FILE *fp);

#include <stdio.h>
int _fputc_r(struct _rent *ptr, int ch, FILE *fp);

#include <stdio.h>
int _fputc_unlocked_r(struct _rent *ptr, int ch, FILE *fp);

Description
fputc converts the argument ch from an int to an unsigned char, then writes it to the file or stream identified by fp.

If the file was opened with append mode (or if the stream cannot support positioning), then the new character goes at the end of the file or stream. Otherwise, the new character is written at the current value of the position indicator, and the position indicator oadvances by one.

For a macro version of this function, see putc.

fputc_unlocked is a non-thread-safe version of fputc. fputc_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fputc_unlocked is equivalent to fputc.

The _fputc_r and _fputc_unlocked_r functions are simply reentrant versions of the above that take an additional reentrant structure argument: ptr.

Returns
If successful, fputc returns its argument ch. If an error intervenes, the result is EOF. You can use ‘ferror(fp)’ to query for errors.

Portability
fputc is required by ANSI C.

fputc_unlocked is a BSD extension also provided by GNU libc.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.21 `fputs`, `fputs_unlocked`—write a character string in a file or stream

Synopsis

#include <stdio.h>
int fputs(const char *restrict s, FILE *restrict fp);

#define _GNU_SOURCE
#include <stdio.h>
int fputs_unlocked(const char *restrict s, FILE *restrict fp);

#include <stdio.h>
int _fputs_r(struct _reent *ptr, const char *restrict s, FILE *restrict fp);

#include <stdio.h>
int _fputs_unlocked_r(struct _reent *ptr, const char *restrict s, FILE *restrict fp);

Description
fputs writes the string at s (but without the trailing null) to the file or stream identified by fp.

fputs_unlocked is a non-thread-safe version of fputs. fputs_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fputs_unlocked is equivalent to fputs.

_fputs_r and _fputs_unlocked_r are simply reentrant versions of the above that take an additional reentrant struct pointer argument: ptr.

Returns
If successful, the result is 0; otherwise, the result is EOF.

Portability
ANSI C requires fputs, but does not specify that the result on success must be 0; any non-negative value is permitted.

fputs_unlocked is a GNU extension.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.22 `fputwc`, `putwc`, `fputwc_unlocked`, `putwc_unlocked`—write a wide character on a stream or file

Synopsis

#include <stdio.h>
#include <wchar.h>
wint_t fputwc(wchar_t wc, FILE *fp);

#define _GNU_SOURCE
#include <stdio.h>
#include <wchar.h>
wint_t fputwc_unlocked(wchar_t wc, FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t _fputwc_r(struct _reent *ptr, wchar_t wc, FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t _fputwc_unlocked_r(struct _reent *ptr, wchar_t wc, FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t putwc(wchar_t wc, FILE *fp);

#define _GNU_SOURCE
#include <stdio.h>
#include <wchar.h>
wint_t putwc_unlocked(wchar_t wc, FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t _putwc_r(struct _reent *ptr, wchar_t wc, FILE *fp);

#include <stdio.h>
#include <wchar.h>
wint_t _putwc_unlocked_r(struct _reent *ptr, wchar_t wc, FILE *fp);

Description
fputwc writes the wide character argument wc to the file or stream identified by fp.

If the file was opened with append mode (or if the stream cannot support positioning), then the new wide character goes at the end of the file or stream. Otherwise, the new wide character is written at the current value of the position indicator, and the position indicator oadvances by one.

fputwc_unlocked is a non-thread-safe version of fputwc. fputwc_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fputwc_unlocked is equivalent to fputwc.

The putwc and putwc_unlocked functions or macros function identically to fputwc and fputwc_unlocked. They may be implemented as a macro, and may evaluate its argument more than once. There is no reason ever to use them.

The _fputwc_r, _putwc_r, _fputwc_unlocked_r, and _putwc_unlocked_r functions are simply reentrant versions of the above that take an additional reentrant structure argument: ptr.

Returns
If successful, fputwc and putwc return their argument wc. If an error intervenes, the result is EOF. You can use ‘ferror(fp)’ to query for errors.

Portability
fputwc and putwc are required by C99 and POSIX.1-2001.

fputwc_unlocked and putwc_unlocked are GNU extensions.

4.23 `fputws`, `fputws_unlocked`—write a wide character string in a file or stream

Synopsis

#include <wchar.h>
int fputws(const wchar_t *__restrict ws, FILE *__restrict fp);

#define _GNU_SOURCE
#include <wchar.h>
int fputws_unlocked(const wchar_t *__restrict ws, FILE *__restrict fp);

#include <wchar.h>
int _fputws_r(struct _reent *ptr, const wchar_t *ws,
    FILE *fp);

#include <wchar.h>
int _fputws_unlocked_r(struct _reent *ptr, const wchar_t *ws,
    FILE *fp);

Description
fputws writes the wide character string at ws (but without the trailing null) to the file or stream identified by fp.

fputws_unlocked is a non-thread-safe version of fputws. fputws_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fputws_unlocked is equivalent to fputws.

_fputws_r and _fputws_unlocked_r are simply reentrant versions of the above that take an additional reentrant struct pointer argument: ptr.

Returns
If successful, the result is a non-negative integer; otherwise, the result is -1 to indicate an error.

Portability
fputws is required by C99 and POSIX.1-2001.

fputws_unlocked is a GNU extension.

4.24 `fread`. `fread_unlocked`—read array elements from a file

Synopsis

#include <stdio.h>
size_t fread(void *restrict buf, size_t size, size_t count,
    FILE *restrict fp);

#define _BSD_SOURCE
#include <stdio.h>
size_t fread_unlocked(void *restrict buf, size_t size, size_t count,
    FILE *restrict fp);

#include <stdio.h>
size_t _fread_r(struct _reent *ptr, void *restrict buf,
    size_t size, size_t count, FILE *restrict fp);

#include <stdio.h>
size_t _fread_unlocked_r(struct _reent *ptr, void *restrict buf,
    size_t size, size_t count, FILE *restrict fp);

Description
fread attempts to copy, from the file or stream identified by fp, count elements (each of size size) into memory, starting at buf. fread may copy fewer elements than count if an error, or end of file, intervenes.

fread also advances the file position indicator (if any) for fp by the number of characters actually read.

fread_unlocked is a non-thread-safe version of fread. fread_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fread_unlocked is equivalent to fread.

_fread_r and _fread_unlocked_r are simply reentrant versions of the above that take an additional reentrant structure pointer argument: ptr.

Returns
The result of fread is the number of elements it succeeded in reading.

Portability
ANSI C requires fread.

fread_unlocked is a BSD extension also provided by GNU libc.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.25 `freopen`—open a file using an existing file descriptor

Synopsis

#include <stdio.h>
FILE *freopen(const char *restrict file, const char *restrict mode,
    FILE *restrict fp);
FILE *_freopen_r(struct _reent *ptr, const char *restrict file,
    const char *restrict mode, FILE *restrict fp);

Description
Use this variant of fopen if you wish to specify a particular file descriptor fp (notably stdin, stdout, or stderr) for the file.

If fp was associated with another file or stream, freopen closes that other file or stream (but ignores any errors while closing it).

file and mode are used just as in fopen.

If file is NULL, the underlying stream is modified rather than closed. The file cannot be given a more permissive access mode (for example, a mode of "w" will fail on a read-only file descriptor), but can change status such as append or binary mode. If modification is not possible, failure occurs.

Returns
If successful, the result is the same as the argument fp. If the file cannot be opened as specified, the result is NULL.

Portability
ANSI C requires freopen.

Supporting OS subroutines required: close, fstat, isatty, lseek, open, read, sbrk, write.

4.26 `fseek`, `fseeko`—set file position

Synopsis

#include <stdio.h>
int fseek(FILE *fp, long offset, int whence)
int fseeko(FILE *fp, off_t offset, int whence)
int _fseek_r(struct _reent *ptr, FILE *fp,
    long offset, int whence)
int _fseeko_r(struct _reent *ptr, FILE *fp,
    off_t offset, int whence)

You can use fseek/fseeko to set the position for the file identified by fp. The value of offset determines the new position, in one of three ways selected by the value of whence (defined as macros in ‘stdio.h’):

SEEK_SET—offset is the absolute file position (an offset from the beginning of the file) desired. offset must be positive.

SEEK_CUR—offset is relative to the current file position. offset can meaningfully be either positive or negative.

SEEK_END—offset is relative to the current end of file. offset can meaningfully be either positive (to increase the size of the file) or negative.

See ftell/ftello to determine the current file position.

Returns
fseek/fseeko return 0 when successful. On failure, the result is EOF. The reason for failure is indicated in errno: either ESPIPE (the stream identified by fp doesn’t support repositioning) or EINVAL (invalid file position).

Portability
ANSI C requires fseek.

fseeko is defined by the Single Unix specification.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.27 `__fsetlocking`—set or query locking mode on FILE stream

Synopsis

#include <stdio.h>
#include <stdio_ext.h>
int __fsetlocking(FILE *fp, int type);

Description
This function sets how the stdio functions handle locking of FILE fp. The following values describe type:

FSETLOCKING_INTERNAL is the default state, where stdio functions automatically lock and unlock the stream.

FSETLOCKING_BYCALLER means that automatic locking in stdio functions is disabled. Applications which set this take all responsibility for file locking themselves.

FSETLOCKING_QUERY returns the current locking mode without changing it.

Returns
__fsetlocking returns the current locking mode of fp.

Portability
This function originates from Solaris and is also provided by GNU libc.

No supporting OS subroutines are required.

4.28 `fsetpos`—restore position of a stream or file

Synopsis

#include <stdio.h>
int fsetpos(FILE *fp, const fpos_t *pos);
int _fsetpos_r(struct _reent *ptr, FILE *fp,
    const fpos_t *pos);

You can use fsetpos to return the file identified by fp to a previous position *pos (after first recording it with fgetpos).

See fseek for a similar facility.

Returns
fgetpos returns 0 when successful. If fgetpos fails, the result is 1. The reason for failure is indicated in errno: either ESPIPE (the stream identified by fp doesn’t support repositioning) or EINVAL (invalid file position).

Portability
ANSI C requires fsetpos, but does not specify the nature of *pos beyond identifying it as written by fgetpos.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.29 `ftell`, `ftello`—return position in a stream or file

Synopsis

#include <stdio.h>
long ftell(FILE *fp);
off_t ftello(FILE *fp);
long _ftell_r(struct _reent *ptr, FILE *fp);
off_t _ftello_r(struct _reent *ptr, FILE *fp);

The result of ftell/ftello is the current position for a file identified by fp. If you record this result, you can later use it with fseek/fseeko to return the file to this position. The difference between ftell and ftello is that ftell returns long and ftello returns off_t.

In the current implementation, ftell/ftello simply uses a character count to represent the file position; this is the same number that would be recorded by fgetpos.

Returns
ftell/ftello return the file position, if possible. If they cannot do this, they return -1L. Failure occurs on streams that do not support positioning; the global errno indicates this condition with the value ESPIPE.

Portability
ftell is required by the ANSI C standard, but the meaning of its result (when successful) is not specified beyond requiring that it be acceptable as an argument to fseek. In particular, other conforming C implementations may return a different result from ftell than what fgetpos records.

ftello is defined by the Single Unix specification.

No supporting OS subroutines are required.

4.30 `funopen`, `fropen`, `fwopen`—open a stream with custom callbacks

Synopsis

#include <stdio.h>
FILE *funopen(const void *cookie,
    int (*readfn) (void *cookie, char *buf, int n),
    int (*writefn) (void *cookie, const char *buf, int n),
    fpos_t (*seekfn) (void *cookie, fpos_t off, int whence),
    int (*closefn) (void *cookie));
FILE *fropen(const void *cookie,
    int (*readfn) (void *cookie, char *buf, int n));
FILE *fwopen(const void *cookie,
    int (*writefn) (void *cookie, const char *buf, int n));

Description
funopen creates a FILE stream where I/O is performed using custom callbacks. At least one of readfn and writefn must be provided, which determines whether the stream behaves with mode <"r">, <"w">, or <"r+">.

readfn should return -1 on failure, or else the number of bytes read (0 on EOF). It is similar to read, except that <int> rather than <size_t> bounds a transaction size, and cookie will be passed as the first argument. A NULL readfn makes attempts to read the stream fail.

writefn should return -1 on failure, or else the number of bytes written. It is similar to write, except that <int> rather than <size_t> bounds a transaction size, and cookie will be passed as the first argument. A NULL writefn makes attempts to write the stream fail.

seekfn should return (fpos_t)-1 on failure, or else the current file position. It is similar to lseek, except that cookie will be passed as the first argument. A NULL seekfn makes the stream behave similarly to a pipe in relation to stdio functions that require positioning. This implementation assumes fpos_t and off_t are the same type.

closefn should return -1 on failure, or 0 on success. It is similar to close, except that cookie will be passed as the first argument. A NULL closefn merely flushes all data then lets fclose succeed. A failed close will still invalidate the stream.

The functions fropen and fwopen are convenience macros around funopen that only use the specified callback.

Returns
The return value is an open FILE pointer on success. On error, NULL is returned, and errno will be set to EINVAL if a function pointer is missing, ENOMEM if the stream cannot be created, or EMFILE if too many streams are already open.

Portability
This function is a newlib extension, copying the prototype from BSD. It is not portable. See also the fopencookie interface from Linux.

Supporting OS subroutines required: sbrk.

4.31 `fwide`—set and determine the orientation of a FILE stream

Synopsis

#include <wchar.h>
int fwide(FILE *fp, int mode)

int _fwide_r(struct _reent *ptr, FILE *fp, int mode)

Description
When mode is zero, the fwide function determines the current orientation of fp. It returns a value > 0 if fp is wide-character oriented, i.e. if wide character I/O is permitted but char I/O is disallowed. It returns a value < 0 if fp is byte oriented, i.e. if char I/O is permitted but wide character I/O is disallowed. It returns zero if fp has no orientation yet; in this case the next I/O operation might change the orientation (to byte oriented if it is a char I/O operation, or to wide-character oriented if it is a wide character I/O operation).

Once a stream has an orientation, it cannot be changed and persists until the stream is closed, unless the stream is re-opened with freopen, which removes the orientation of the stream.

When mode is non-zero, the fwide function first attempts to set fp’s orientation (to wide-character oriented if mode > 0, or to byte oriented if mode < 0). It then returns a value denoting the current orientation, as above.

Returns
The fwide function returns fp’s orientation, after possibly changing it. A return value > 0 means wide-character oriented. A return value < 0 means byte oriented. A return value of zero means undecided.

Portability
C99, POSIX.1-2001.

4.32 `fwrite`, `fwrite_unlocked`—write array elements

Synopsis

#include <stdio.h>
size_t fwrite(const void *restrict buf, size_t size,
    size_t count, FILE *restrict fp);

#define _BSD_SOURCE
#include <stdio.h>
size_t fwrite_unlocked(const void *restrict buf, size_t size,
    size_t count, FILE *restrict fp);

#include <stdio.h>
size_t _fwrite_r(struct _reent *ptr, const void *restrict buf, size_t size,
    size_t count, FILE *restrict fp);

#include <stdio.h>
size_t _fwrite_unlocked_r(struct _reent *ptr, const void *restrict buf, size_t size,
    size_t count, FILE *restrict fp);

Description
fwrite attempts to copy, starting from the memory location buf, count elements (each of size size) into the file or stream identified by fp. fwrite may copy fewer elements than count if an error intervenes.

fwrite also advances the file position indicator (if any) for fp by the number of characters actually written.

fwrite_unlocked is a non-thread-safe version of fwrite. fwrite_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then fwrite_unlocked is equivalent to fwrite.

_fwrite_r and _fwrite_unlocked_r are simply reentrant versions of the above that take an additional reentrant structure argument: ptr.

Returns
If fwrite succeeds in writing all the elements you specify, the result is the same as the argument count. In any event, the result is the number of complete elements that fwrite copied to the file.

Portability
ANSI C requires fwrite.

fwrite_unlocked is a BSD extension also provided by GNU libc.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.33 `getc`—read a character (macro)

Synopsis

#include <stdio.h>
int getc(FILE *fp);

#include <stdio.h>
int _getc_r(struct _reent *ptr, FILE *fp);

Description
getc is a macro, defined in stdio.h. You can use getc to get the next single character from the file or stream identified by fp. As a side effect, getc advances the file’s current position indicator.

For a subroutine version of this macro, see fgetc.

The _getc_r function is simply the reentrant version of getc which passes an additional reentrancy structure pointer argument: ptr.

You can distinguish the two situations that cause an EOF result by using the ferror and feof functions.

Portability
ANSI C requires getc; it suggests, but does not require, that getc be implemented as a macro. The standard explicitly permits macro implementations of getc to use the argument more than once; therefore, in a portable program, you should not use an expression with side effects as the getc argument.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.34 `getc_unlocked`—non-thread-safe version of getc (macro)

Synopsis

#include <stdio.h>
int getc_unlocked(FILE *fp);

#include <stdio.h>
int _getc_unlocked_r(FILE *fp);

Description
getc_unlocked is a non-thread-safe version of getc declared in stdio.h. getc_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). These functions may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the ( FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then getc_unlocked is equivalent to getc.

The _getc_unlocked_r function is simply the reentrant version of get_unlocked which passes an additional reentrancy structure pointer argument: ptr.

Returns
See getc.

Portability
POSIX 1003.1 requires getc_unlocked. getc_unlocked may be implemented as a macro, so arguments should not have side-effects.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.35 `getchar`—read a character (macro)

Synopsis

#include <stdio.h>
int getchar(void);

int _getchar_r(struct _reent *reent);

Description
getchar is a macro, defined in stdio.h. You can use getchar to get the next single character from the standard input stream. As a side effect, getchar advances the standard input’s current position indicator.

The alternate function _getchar_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

You can distinguish the two situations that cause an EOF result by using ‘ferror(stdin)’ and ‘feof(stdin)’.

Portability
ANSI C requires getchar; it suggests, but does not require, that getchar be implemented as a macro.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.36 `getchar_unlocked`—non-thread-safe version of getchar (macro)

Synopsis

#include <stdio.h>
int getchar_unlocked();

#include <stdio.h>
int _getchar_unlocked_r(struct _reent *ptr);

Description
getchar_unlocked is a non-thread-safe version of getchar declared in stdio.h. getchar_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). These functions may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the ( FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then getchar_unlocked is equivalent to getchar.

The _getchar_unlocked_r function is simply the reentrant version of getchar_unlocked which passes an addtional reentrancy structure pointer argument: ptr.

Returns
See getchar.

Portability
POSIX 1003.1 requires getchar_unlocked. getchar_unlocked may be implemented as a macro.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.37 `getdelim`—read a line up to a specified line delimiter

Synopsis

#include <stdio.h>
int getdelim(char **bufptr, size_t *n,
    int delim, FILE *fp);

Description
getdelim reads a file fp up to and possibly including a specified delimiter delim. The line is read into a buffer pointed to by bufptr and designated with size *n. If the buffer is not large enough, it will be dynamically grown by getdelim. As the buffer is grown, the pointer to the size n will be updated.

Returns
getdelim returns -1 if no characters were successfully read; otherwise, it returns the number of bytes successfully read. At end of file, the result is nonzero.

Portability
getdelim is a glibc extension.

No supporting OS subroutines are directly required.

4.38 `getline`—read a line from a file

Synopsis

#include <stdio.h>
ssize_t getline(char **bufptr, size_t *n, FILE *fp);

Description
getline reads a file fp up to and possibly including the newline character. The line is read into a buffer pointed to by bufptr and designated with size *n. If the buffer is not large enough, it will be dynamically grown by getdelim. As the buffer is grown, the pointer to the size n will be updated.

getline is equivalent to getdelim(bufptr, n, ’\n’, fp);

Returns
getline returns -1 if no characters were successfully read, otherwise, it returns the number of bytes successfully read. at end of file, the result is nonzero.

Portability
getline is a glibc extension.

No supporting OS subroutines are directly required.

4.39 `gets`—get character string (obsolete, use `fgets` instead)

Synopsis

#include <stdio.h>

char *gets(char *buf);

char *_gets_r(struct _reent *reent, char *buf);

Description
Reads characters from standard input until a newline is found. The characters up to the newline are stored in buf. The newline is discarded, and the buffer is terminated with a 0.

This is a dangerous function, as it has no way of checking the amount of space available in buf. One of the attacks used by the Internet Worm of 1988 used this to overrun a buffer allocated on the stack of the finger daemon and overwrite the return address, causing the daemon to execute code downloaded into it over the connection.

The alternate function _gets_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
gets returns the buffer passed to it, with the data filled in. If end of file occurs with some data already accumulated, the data is returned with no other indication. If end of file occurs with no data in the buffer, NULL is returned.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.40 `getw`—read a word (int)

Synopsis

#include <stdio.h>
int getw(FILE *fp);

Description
getw is a function, defined in stdio.h. You can use getw to get the next word from the file or stream identified by fp. As a side effect, getw advances the file’s current position indicator.

Returns
The next word (read as an int), unless there is no more data or the host system reports a read error; in either of these situations, getw returns EOF. Since EOF is a valid int, you must use ferror or feof to distinguish these situations.

Portability
getw is a remnant of K&R C; it is not part of any ISO C Standard. fread should be used instead. In fact, this implementation of getw is based upon fread.

Supporting OS subroutines required: fread.

4.41 `getwchar`, `getwchar_unlocked`—read a wide character from standard input

Synopsis

#include <wchar.h>
wint_t getwchar(void);

#define _GNU_SOURCE
#include <wchar.h>
wint_t getwchar_unlocked(void);

#include <wchar.h>
wint_t _getwchar_r(struct _reent *reent);

#include <wchar.h>
wint_t _getwchar_unlocked_r(struct _reent *reent);

Description
getwchar function or macro is the wide character equivalent of the getchar function. You can use getwchar to get the next wide character from the standard input stream. As a side effect, getwchar advances the standard input’s current position indicator.

getwchar_unlocked is a non-thread-safe version of getwchar. getwchar_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then getwchar_unlocked is equivalent to getwchar.

The alternate functions _getwchar_r and _getwchar_unlocked_r are reentrant versions of the above. The extra argument reent is a pointer to a reentrancy structure.

Returns
The next wide character cast to wint_t, unless there is no more data, or the host system reports a read error; in either of these situations, getwchar returns WEOF.

You can distinguish the two situations that cause an WEOF result by using ‘ferror(stdin)’ and ‘feof(stdin)’.

Portability
getwchar is required by C99.

getwchar_unlocked is a GNU extension.

4.42 `mktemp`, `mkstemp`, `mkostemp`, `mkstemps`,

Synopsis

#include <stdlib.h>
char *mktemp(char *path);
char *mkdtemp(char *path);
int mkstemp(char *path);
int mkstemps(char *path, int suffixlen);
int mkostemp(char *path, int flags);
int mkostemps(char *path, int suffixlen, int flags);

char *_mktemp_r(struct _reent *reent, char *path);
char *_mkdtemp_r(struct _reent *reent, char *path);
int *_mkstemp_r(struct _reent *reent, char *path);
int *_mkstemps_r(struct _reent *reent, char *path, int len);
int *_mkostemp_r(struct _reent *reent, char *path,
    int flags);
int *_mkostemps_r(struct _reent *reent, char *path, int len,
    int flags);

Description
mktemp, mkstemp, and mkstemps attempt to generate a file name that is not yet in use for any existing file. mkstemp and mkstemps create the file and open it for reading and writing; mktemp simply generates the file name (making mktemp a security risk). mkostemp and mkostemps allow the addition of other open flags, such as O_CLOEXEC, O_APPEND, or O_SYNC. On platforms with a separate text mode, mkstemp forces O_BINARY, while mkostemp allows the choice between O_BINARY, O_TEXT, or 0 for default. mkdtemp attempts to create a directory instead of a file, with a permissions mask of 0700.

You supply a simple pattern for the generated file name, as the string at path. The pattern should be a valid filename (including path information if you wish) ending with at least six ‘X’ characters. The generated filename will match the leading part of the name you supply, with the trailing ‘X’ characters replaced by some combination of digits and letters. With mkstemps, the ‘X’ characters end suffixlen bytes before the end of the string.

The alternate functions _mktemp_r, _mkdtemp_r, _mkstemp_r, _mkostemp_r, _mkostemps_r, and _mkstemps_r are reentrant versions. The extra argument reent is a pointer to a reentrancy structure.

Returns
mktemp returns the pointer path to the modified string representing an unused filename, unless it could not generate one, or the pattern you provided is not suitable for a filename; in that case, it returns NULL. Be aware that there is an inherent race between generating the name and attempting to create a file by that name; you are advised to use O_EXCL|O_CREAT.

mkdtemp returns the pointer path to the modified string if the directory was created, otherwise it returns NULL.

mkstemp, mkstemps, mkostemp, and mkostemps return a file descriptor to the newly created file, unless it could not generate an unused filename, or the pattern you provided is not suitable for a filename; in that case, it returns -1.

Portability
ANSI C does not require either mktemp or mkstemp; the System V Interface Definition requires mktemp as of Issue 2. POSIX 2001 requires mkstemp, and POSIX 2008 requires mkdtemp while deprecating mktemp. mkstemps, mkostemp, and mkostemps are not standardized.

Supporting OS subroutines required: getpid, mkdir, open, stat.

4.43 `open_memstream`, `open_wmemstream`—open a write stream around an arbitrary-length string

Synopsis

#include <stdio.h>
FILE *open_memstream(char **restrict buf,
    size_t *restrict size);

#include <wchar.h>
FILE *open_wmemstream(wchar_t **restrict buf,
    size_t *restrict size);

Description
open_memstream creates a seekable, byte-oriented FILE stream that wraps an arbitrary-length buffer, created as if by malloc. The current contents of *buf are ignored; this implementation uses *size as a hint of the maximum size expected, but does not fail if the hint was wrong. The parameters buf and size are later stored through following any call to fflush or fclose, set to the current address and usable size of the allocated string; although after fflush, the pointer is only valid until another stream operation that results in a write. Behavior is undefined if the user alters either *buf or *size prior to fclose.

open_wmemstream is like open_memstream just with the associated stream being wide-oriented. The size set in size in subsequent operations is the number of wide characters.

The stream is write-only, since the user can directly read *buf after a flush; see fmemopen for a way to wrap a string with a readable stream. The user is responsible for calling free on the final *buf after fclose.

Any time the stream is flushed, a NUL byte is written at the current position (but is not counted in the buffer length), so that the string is always NUL-terminated after at most *size bytes (or wide characters in case of open_wmemstream). However, data previously written beyond the current stream offset is not lost, and the NUL value written during a flush is restored to its previous value when seeking elsewhere in the string.

Returns
The return value is an open FILE pointer on success. On error, NULL is returned, and errno will be set to EINVAL if buf or size is NULL, ENOMEM if memory could not be allocated, or EMFILE if too many streams are already open.

Portability
POSIX.1-2008

Supporting OS subroutines required: sbrk.

4.44 `perror`—print an error message on standard error

Synopsis

#include <stdio.h>
void perror(char *prefix);

void _perror_r(struct _reent *reent, char *prefix);

Description
Use perror to print (on standard error) an error message corresponding to the current value of the global variable errno. Unless you use NULL as the value of the argument prefix, the error message will begin with the string at prefix, followed by a colon and a space (: ). The remainder of the error message is one of the strings described for strerror.

The alternate function _perror_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
perror returns no result.

Portability
ANSI C requires perror, but the strings issued vary from one implementation to another.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.45 `putc`—write a character (macro)

Synopsis

#include <stdio.h>
int putc(int ch, FILE *fp);

#include <stdio.h>
int _putc_r(struct _reent *ptr, int ch, FILE *fp);

Description
putc is a macro, defined in stdio.h. putc writes the argument ch to the file or stream identified by fp, after converting it from an int to an unsigned char.

For a subroutine version of this macro, see fputc.

The _putc_r function is simply the reentrant version of putc that takes an additional reentrant structure argument: ptr.

Returns
If successful, putc returns its argument ch. If an error intervenes, the result is EOF. You can use ‘ferror(fp)’ to query for errors.

Portability
ANSI C requires putc; it suggests, but does not require, that putc be implemented as a macro. The standard explicitly permits macro implementations of putc to use the fp argument more than once; therefore, in a portable program, you should not use an expression with side effects as this argument.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.46 `putc_unlocked`—non-thread-safe version of putc (macro)

Synopsis

#include <stdio.h>
int putc_unlocked(int ch, FILE *fp);

#include <stdio.h>
int _putc_unlocked_r(struct _reent *ptr, int ch, FILE *fp);

Description
putc_unlocked is a non-thread-safe version of putc declared in stdio.h. putc_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). These functions may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the ( FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then putc_unlocked is equivalent to putc.

The function _putc_unlocked_r is simply the reentrant version of putc_unlocked that takes an additional reentrant structure pointer argument: ptr.

Returns
See putc.

Portability
POSIX 1003.1 requires putc_unlocked. putc_unlocked may be implemented as a macro, so arguments should not have side-effects.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.47 `putchar`—write a character (macro)

Synopsis

#include <stdio.h>
int putchar(int ch);

int _putchar_r(struct _reent *reent, int ch);

Description
putchar is a macro, defined in stdio.h. putchar writes its argument to the standard output stream, after converting it from an int to an unsigned char.

The alternate function _putchar_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
If successful, putchar returns its argument ch. If an error intervenes, the result is EOF. You can use ‘ferror(stdin)’ to query for errors.

Portability
ANSI C requires putchar; it suggests, but does not require, that putchar be implemented as a macro.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.48 `putchar_unlocked`—non-thread-safe version of putchar (macro)

Synopsis

#include <stdio.h>
int putchar_unlocked(int ch);

Description
putchar_unlocked is a non-thread-safe version of putchar declared in stdio.h. putchar_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). These functions may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the ( FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then putchar_unlocked is equivalent to putchar.

Returns
See putchar.

Portability
POSIX 1003.1 requires putchar_unlocked. putchar_unlocked may be implemented as a macro.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.49 `puts`—write a character string

Synopsis

#include <stdio.h>
int puts(const char *s);

int _puts_r(struct _reent *reent, const char *s);

Description
puts writes the string at s (followed by a newline, instead of the trailing null) to the standard output stream.

The alternate function _puts_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
If successful, the result is a nonnegative integer; otherwise, the result is EOF.

Portability
ANSI C requires puts, but does not specify that the result on success must be 0; any non-negative value is permitted.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.50 `putw`—write a word (int)

Synopsis

#include <stdio.h>
int putw(int w, FILE *fp);

Description
putw is a function, defined in stdio.h. You can use putw to write a word to the file or stream identified by fp. As a side effect, putw advances the file’s current position indicator.

Returns
Zero on success, EOF on failure.

Portability
putw is a remnant of K&R C; it is not part of any ISO C Standard. fwrite should be used instead. In fact, this implementation of putw is based upon fwrite.

Supporting OS subroutines required: fwrite.

4.51 `putwchar`, `putwchar_unlocked`—write a wide character to standard output

Synopsis

#include <wchar.h>
wint_t putwchar(wchar_t wc);

#include <wchar.h>
wint_t putwchar_unlocked(wchar_t wc);

#include <wchar.h>
wint_t _putwchar_r(struct _reent *reent, wchar_t wc);

#include <wchar.h>
wint_t _putwchar_unlocked_r(struct _reent *reent, wchar_t wc);

Description
The putwchar function or macro is the wide-character equivalent of the putchar function. It writes the wide character wc to stdout.

putwchar_unlocked is a non-thread-safe version of putwchar. putwchar_unlocked may only safely be used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). This function may safely be used in a multi-threaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions. If threads are disabled, then putwchar_unlocked is equivalent to putwchar.

The alternate functions _putwchar_r and _putwchar_unlocked_r are reentrant versions of the above. The extra argument reent is a pointer to a reentrancy structure.

Returns
If successful, putwchar returns its argument wc. If an error intervenes, the result is EOF. You can use ‘ferror(stdin)’ to query for errors.

Portability
putwchar is required by C99.

putwchar_unlocked is a GNU extension.

4.52 `remove`—delete a file’s name

Synopsis

#include <stdio.h>
int remove(char *filename);

int _remove_r(struct _reent *reent, char *filename);

Description
Use remove to dissolve the association between a particular filename (the string at filename) and the file it represents. After calling remove with a particular filename, you will no longer be able to open the file by that name.

In this implementation, you may use remove on an open file without error; existing file descriptors for the file will continue to access the file’s data until the program using them closes the file.

The alternate function _remove_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
remove returns 0 if it succeeds, -1 if it fails.

Portability
ANSI C requires remove, but only specifies that the result on failure be nonzero. The behavior of remove when you call it on an open file may vary among implementations.

Supporting OS subroutine required: unlink.

4.53 `rename`—rename a file

Synopsis

#include <stdio.h>
int rename(const char *old, const char *new);

Description
Use rename to establish a new name (the string at new) for a file now known by the string at old. After a successful rename, the file is no longer accessible by the string at old.

If rename fails, the file named *old is unaffected. The conditions for failure depend on the host operating system.

Returns
The result is either 0 (when successful) or -1 (when the file could not be renamed).

Portability
ANSI C requires rename, but only specifies that the result on failure be nonzero. The effects of using the name of an existing file as *new may vary from one implementation to another.

Supporting OS subroutines required: link, unlink, or rename.

4.54 `rewind`—reinitialize a file or stream

Synopsis

#include <stdio.h>
void rewind(FILE *fp);
void _rewind_r(struct _reent *ptr, FILE *fp);

Description
rewind returns the file position indicator (if any) for the file or stream identified by fp to the beginning of the file. It also clears any error indicator and flushes any pending output.

Returns
rewind does not return a result.

Portability
ANSI C requires rewind.

No supporting OS subroutines are required.

4.55 `setbuf`—specify full buffering for a file or stream

Synopsis

#include <stdio.h>
void setbuf(FILE *fp, char *buf);

Description
setbuf specifies that output to the file or stream identified by fp should be fully buffered. All output for this file will go to a buffer (of size BUFSIZ, specified in ‘stdio.h’). Output will be passed on to the host system only when the buffer is full, or when an input operation intervenes.

You may, if you wish, supply your own buffer by passing a pointer to it as the argument buf. It must have size BUFSIZ. You can also use NULL as the value of buf, to signal that the setbuf function is to allocate the buffer.

Warnings
You may only use setbuf before performing any file operation other than opening the file.

If you supply a non-null buf, you must ensure that the associated storage continues to be available until you close the stream identified by fp.

Returns
setbuf does not return a result.

Portability
Both ANSI C and the System V Interface Definition (Issue 2) require setbuf. However, they differ on the meaning of a NULL buffer pointer: the SVID issue 2 specification says that a NULL buffer pointer requests unbuffered output. For maximum portability, avoid NULL buffer pointers.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.56 `setbuffer`—specify full buffering for a file or stream with size

Synopsis

#include <stdio.h>
void setbuffer(FILE *fp, char *buf, int size);

Description
setbuffer specifies that output to the file or stream identified by fp should be fully buffered. All output for this file will go to a buffer (of size size). Output will be passed on to the host system only when the buffer is full, or when an input operation intervenes.

You may, if you wish, supply your own buffer by passing a pointer to it as the argument buf. It must have size size. You can also use NULL as the value of buf, to signal that the setbuffer function is to allocate the buffer.

Warnings
You may only use setbuffer before performing any file operation other than opening the file.

If you supply a non-null buf, you must ensure that the associated storage continues to be available until you close the stream identified by fp.

Returns
setbuffer does not return a result.

Portability
This function comes from BSD not ANSI or POSIX.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.57 `setlinebuf`—specify line buffering for a file or stream

Synopsis

#include <stdio.h>
void setlinebuf(FILE *fp);

Description
setlinebuf specifies that output to the file or stream identified by fp should be line buffered. This causes the file or stream to pass on output to the host system at every newline, as well as when the buffer is full, or when an input operation intervenes.

Warnings
You may only use setlinebuf before performing any file operation other than opening the file.

Returns
setlinebuf returns as per setvbuf.

Portability
This function comes from BSD not ANSI or POSIX.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.58 `setvbuf`—specify file or stream buffering

Synopsis

#include <stdio.h>
int setvbuf(FILE *fp, char *buf,
    int mode, size_t size);

Description
Use setvbuf to specify what kind of buffering you want for the file or stream identified by fp, by using one of the following values (from stdio.h) as the mode argument:

_IONBF: Do not use a buffer: send output directly to the host system for the file or stream identified by fp.
_IOFBF: Use full output buffering: output will be passed on to the host system only when the buffer is full, or when an input operation intervenes.
_IOLBF: Use line buffering: pass on output to the host system at every newline, as well as when the buffer is full, or when an input operation intervenes.

Use the size argument to specify how large a buffer you wish. You can supply the buffer itself, if you wish, by passing a pointer to a suitable area of memory as buf. Otherwise, you may pass NULL as the buf argument, and setvbuf will allocate the buffer.

Warnings
You may only use setvbuf before performing any file operation other than opening the file.

If you supply a non-null buf, you must ensure that the associated storage continues to be available until you close the stream identified by fp.

Returns
A 0 result indicates success, EOF failure (invalid mode or size can cause failure).

Portability
Both ANSI C and the System V Interface Definition (Issue 2) require setvbuf. However, they differ on the meaning of a NULL buffer pointer: the SVID issue 2 specification says that a NULL buffer pointer requests unbuffered output. For maximum portability, avoid NULL buffer pointers.

Both specifications describe the result on failure only as a nonzero value.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.59 `siprintf`, `fiprintf`, `iprintf`, `sniprintf`, `asiprintf`, `asniprintf`—format output (integer only)

Synopsis

#include <stdio.h>

int iprintf(const char *format, ...);
int fiprintf(FILE *fd, const char *format , ...);
int siprintf(char *str, const char *format, ...);
int sniprintf(char *str, size_t size, const char *format, 
    ...);
int asiprintf(char **strp, const char *format, ...);
char *asniprintf(char *str, size_t *size, 
    const char *format, ...);

int _iprintf_r(struct _reent *ptr, const char *format, ...);
int _fiprintf_r(struct _reent *ptr, FILE *fd,
    const char *format, ...);
int _siprintf_r(struct _reent *ptr, char *str,
    const char *format, ...);
int _sniprintf_r(struct _reent *ptr, char *str, size_t size,
    const char *format, ...);
int _asiprintf_r(struct _reent *ptr, char **strp,
    const char *format, ...);
char *_asniprintf_r(struct _reent *ptr, char *str,
    size_t *size, const char *format, ...);

Description
iprintf, fiprintf, siprintf, sniprintf, asiprintf, and asniprintf are the same as printf, fprintf, sprintf, snprintf, asprintf, and asnprintf, respectively, except that they restrict usage to non-floating-point format specifiers.

_iprintf_r, _fiprintf_r, _asiprintf_r, _siprintf_r, _sniprintf_r, _asniprintf_r are simply reentrant versions of the functions above.

Returns
Similar to printf, fprintf, sprintf, snprintf, asprintf, and asnprintf.

Portability
iprintf, fiprintf, siprintf, sniprintf, asiprintf, and asniprintf are newlib extensions.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.60 `siscanf`, `fiscanf`, `iscanf`—scan and format non-floating input

Synopsis

#include <stdio.h>

int iscanf(const char *format, ...);
int fiscanf(FILE *fd, const char *format, ...);
int siscanf(const char *str, const char *format, ...);

int _iscanf_r(struct _reent *ptr, const char *format, ...);
int _fiscanf_r(struct _reent *ptr, FILE *fd, 
    const char *format, ...);
int _siscanf_r(struct _reent *ptr, const char *str,
    const char *format, ...);

Description
iscanf, fiscanf, and siscanf are the same as scanf, fscanf, and sscanf respectively, only that they restrict the available formats to non-floating-point format specifiers.

The routines _iscanf_r, _fiscanf_r, and _siscanf_r are reentrant versions of iscanf, fiscanf, and siscanf that take an additional first argument pointing to a reentrancy structure.

Returns
iscanf returns the number of input fields successfully scanned, converted and stored; the return value does not include scanned fields which were not stored.

If iscanf attempts to read at end-of-file, the return value is EOF.

If no fields were stored, the return value is 0.

Portability
iscanf, fiscanf, and siscanf are newlib extensions.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.61 `sprintf`, `fprintf`, `printf`, `snprintf`, `asprintf`, `asnprintf`—format output

Synopsis

#include <stdio.h>

int printf(const char *restrict format, ...);
int fprintf(FILE *restrict fd, const char *restrict format, ...);
int sprintf(char *restrict str, const char *restrict format, ...);
int snprintf(char *restrict str, size_t size, const char *restrict format,
    ...);
int asprintf(char **restrict strp, const char *restrict format, ...);
char *asnprintf(char *restrict str, size_t *restrict size, const char *restrict format,
    ...);

int _printf_r(struct _reent *ptr, const char *restrict format, ...);
int _fprintf_r(struct _reent *ptr, FILE *restrict fd,
    const char *restrict format, ...);
int _sprintf_r(struct _reent *ptr, char *restrict str,
    const char *restrict format, ...);
int _snprintf_r(struct _reent *ptr, char *restrict str, size_t size,
    const char *restrict format, ...);
int _asprintf_r(struct _reent *ptr, char **restrict strp,
    const char *restrict format, ...);
char *_asnprintf_r(struct _reent *ptr, char *restrict str,
    size_t *restrict size, const char *restrict format, ...);

Description
printf accepts a series of arguments, applies to each a format specifier from *format, and writes the formatted data to stdout, without a terminating NUL character. The behavior of printf is undefined if there are not enough arguments for the format. printf returns when it reaches the end of the format string. If there are more arguments than the format requires, excess arguments are ignored.

fprintf is like printf, except that output is directed to the stream fd rather than stdout.

sprintf is like printf, except that output is directed to the buffer str, and a terminating NUL is output. Behavior is undefined if more output is generated than the buffer can hold.

snprintf is like sprintf, except that output is limited to at most size bytes, including the terminating NUL. As a special case, if size is 0, str can be NULL, and snprintf merely calculates how many bytes would be printed.

asprintf is like sprintf, except that the output is stored in a dynamically allocated buffer, pstr, which should be freed later with free.

asnprintf is like sprintf, except that the return type is either the original str if it was large enough, or a dynamically allocated string if the output exceeds *size; the length of the result is returned in *size. When dynamic allocation occurs, the contents of the original str may have been modified.

For sprintf, snprintf, and asnprintf, the behavior is undefined if the output *str overlaps with one of the arguments. Behavior is also undefined if the argument for %n within *format overlaps another argument.

format is a pointer to a character string containing two types of objects: ordinary characters (other than %), which are copied unchanged to the output, and conversion specifications, each of which is introduced by %. (To include % in the output, use %% in the format string.) A conversion specification has the following form:

       %[pos][flags][width][.prec][size]type

The fields of the conversion specification have the following meanings:

pos
Conversions normally consume arguments in the order that they are presented. However, it is possible to consume arguments out of order, and reuse an argument for more than one conversion specification (although the behavior is undefined if the same argument is requested with different types), by specifying pos, which is a decimal integer followed by ’$’. The integer must be between 1 and <NL_ARGMAX> from limits.h, and if argument %n$ is requested, all earlier arguments must be requested somewhere within format. If positional parameters are used, then all conversion specifications except for %% must specify a position. This positional parameters method is a POSIX extension to the C standard definition for the functions.
flags
flags is an optional sequence of characters which control output justification, numeric signs, decimal points, trailing zeros, and octal and hex prefixes. The flag characters are minus (-), plus (+), space ( ), zero (0), sharp (#), and quote ('). They can appear in any combination, although not all flags can be used for all conversion specification types.

'

A POSIX extension to the C standard. However, this implementation presently treats it as a no-op, which is the default behavior for the C locale, anyway. (If it did what it is supposed to, when type were i, d, u, f, F, g, or G, the integer portion of the conversion would be formatted with thousands’ grouping wide characters.)

-

The result of the conversion is left justified, and the right is padded with blanks. If you do not use this flag, the result is right justified, and padded on the left.

+

The result of a signed conversion (as determined by type of d, i, a, A, e, E, f, F, g, or G) will always begin with a plus or minus sign. (If you do not use this flag, positive values do not begin with a plus sign.)

" " (space)

If the first character of a signed conversion specification is not a sign, or if a signed conversion results in no characters, the result will begin with a space. If the space ( ) flag and the plus (+) flag both appear, the space flag is ignored.

0

If the type character is d, i, o, u, x, X, a, A, e, E, f, F, g, or G: leading zeros are used to pad the field width (following any indication of sign or base); no spaces are used for padding. If the zero (0) and minus (-) flags both appear, the zero (0) flag will be ignored. For d, i, o, u, x, and X conversions, if a precision prec is specified, the zero (0) flag is ignored.

Note that 0 is interpreted as a flag, not as the beginning of a field width.

#

The result is to be converted to an alternative form, according to the type character:

o

Increases precision to force the first digit of the result to be a zero.

x

A non-zero result will have a 0x prefix.

X

A non-zero result will have a 0X prefix.

a, A, e, E, f, or F

The result will always contain a decimal point even if no digits follow the point. (Normally, a decimal point appears only if a digit follows it.) Trailing zeros are removed.

g or G

The result will always contain a decimal point even if no digits follow the point. Trailing zeros are not removed.

all others

Undefined.
width
width is an optional minimum field width. You can either specify it directly as a decimal integer, or indirectly by using instead an asterisk (*), in which case an int argument is used as the field width. If positional arguments are used, then the width must also be specified positionally as *m$, with m as a decimal integer. Negative field widths are treated as specifying the minus (-) flag for left justfication, along with a positive field width. The resulting format may be wider than the specified width.
prec
prec is an optional field; if present, it is introduced with ‘.’ (a period). You can specify the precision either directly as a decimal integer or indirectly by using an asterisk (*), in which case an int argument is used as the precision. If positional arguments are used, then the precision must also be specified positionally as *m$, with m as a decimal integer. Supplying a negative precision is equivalent to omitting the precision. If only a period is specified the precision is zero. The effect depends on the conversion type.

d, i, o, u, x, or X

Minimum number of digits to appear. If no precision is given, defaults to 1.

a or A

Number of digits to appear after the decimal point. If no precision is given, the precision defaults to the minimum needed for an exact representation.

e, E, f or F

Number of digits to appear after the decimal point. If no precision is given, the precision defaults to 6.

g or G

Maximum number of significant digits. A precision of 0 is treated the same as a precision of 1. If no precision is given, the precision defaults to 6.

s or S

Maximum number of characters to print from the string. If no precision is given, the entire string is printed.

all others

undefined.
size
size is an optional modifier that changes the data type that the corresponding argument has. Behavior is unspecified if a size is given that does not match the type.

hh

With d, i, o, u, x, or X, specifies that the argument should be converted to a signed char or unsigned char before printing.

With n, specifies that the argument is a pointer to a signed char.

h

With d, i, o, u, x, or X, specifies that the argument should be converted to a short or unsigned short before printing.

With n, specifies that the argument is a pointer to a short.

l

With d, i, o, u, x, or X, specifies that the argument is a long or unsigned long.

With c, specifies that the argument has type wint_t.

With s, specifies that the argument is a pointer to wchar_t.

With n, specifies that the argument is a pointer to a long.

With a, A, e, E, f, F, g, or G, has no effect (because of vararg promotion rules, there is no need to distinguish between float and double).

ll

With d, i, o, u, x, or X, specifies that the argument is a long long or unsigned long long.

With n, specifies that the argument is a pointer to a long long.

j

With d, i, o, u, x, or X, specifies that the argument is an intmax_t or uintmax_t.

With n, specifies that the argument is a pointer to an intmax_t.

z

With d, i, o, u, x, or X, specifies that the argument is a size_t.

With n, specifies that the argument is a pointer to a size_t.

t

With d, i, o, u, x, or X, specifies that the argument is a ptrdiff_t.

With n, specifies that the argument is a pointer to a ptrdiff_t.

L

With a, A, e, E, f, F, g, or G, specifies that the argument is a long double.
type
type specifies what kind of conversion printf performs. Here is a table of these:

%

Prints the percent character (%).

c

Prints arg as single character. If the l size specifier is in effect, a multibyte character is printed.

C

Short for %lc. A POSIX extension to the C standard.

s

Prints the elements of a pointer to char until the precision or a null character is reached. If the l size specifier is in effect, the pointer is to an array of wchar_t, and the string is converted to multibyte characters before printing.

S

Short for %ls. A POSIX extension to the C standard.

d or i

Prints a signed decimal integer; takes an int. Leading zeros are inserted as necessary to reach the precision. A value of 0 with a precision of 0 produces an empty string.

D

Newlib extension, short for %ld.

o

Prints an unsigned octal integer; takes an unsigned. Leading zeros are inserted as necessary to reach the precision. A value of 0 with a precision of 0 produces an empty string.

O

Newlib extension, short for %lo.

u

Prints an unsigned decimal integer; takes an unsigned. Leading zeros are inserted as necessary to reach the precision. A value of 0 with a precision of 0 produces an empty string.

U

Newlib extension, short for %lu.

x

Prints an unsigned hexadecimal integer (using abcdef as digits beyond 9); takes an unsigned. Leading zeros are inserted as necessary to reach the precision. A value of 0 with a precision of 0 produces an empty string.

X

Like x, but uses ABCDEF as digits beyond 9.

f

Prints a signed value of the form [-]9999.9999, with the precision determining how many digits follow the decimal point; takes a double (remember that float promotes to double as a vararg). The low order digit is rounded to even. If the precision results in at most DECIMAL_DIG digits, the result is rounded correctly; if more than DECIMAL_DIG digits are printed, the result is only guaranteed to round back to the original value.

If the value is infinite, the result is inf, and no zero padding is performed. If the value is not a number, the result is nan, and no zero padding is performed.

F

Like f, but uses INF and NAN for non-finite numbers.

e

Prints a signed value of the form [-]9.9999e[+|-]999; takes a double. The digit before the decimal point is non-zero if the value is non-zero. The precision determines how many digits appear between . and e, and the exponent always contains at least two digits. The value zero has an exponent of zero. If the value is not finite, it is printed like f.

E

Like e, but using E to introduce the exponent, and like F for non-finite values.

g

Prints a signed value in either f or e form, based on the given value and precision—an exponent less than -4 or greater than the precision selects the e form. Trailing zeros and the decimal point are printed only if necessary; takes a double.

G

Like g, except use F or E form.

a

Prints a signed value of the form [-]0x1.ffffp[+|-]9; takes a double. The letters abcdef are used for digits beyond 9. The precision determines how many digits appear after the decimal point. The exponent contains at least one digit, and is a decimal value representing the power of 2; a value of 0 has an exponent of 0. Non-finite values are printed like f.

A

Like a, except uses X, P, and ABCDEF instead of lower case.

n

Takes a pointer to int, and stores a count of the number of bytes written so far. No output is created.

p

Takes a pointer to void, and prints it in an implementation-defined format. This implementation is similar to %#tx), except that 0x appears even for the NULL pointer.

m

Prints the output of strerror(errno); no argument is required. A GNU extension.

_printf_r, _fprintf_r, _asprintf_r, _sprintf_r, _snprintf_r, _asnprintf_r are simply reentrant versions of the functions above.

Returns
On success, sprintf and asprintf return the number of bytes in the output string, except the concluding NUL is not counted. snprintf returns the number of bytes that would be in the output string, except the concluding NUL is not counted. printf and fprintf return the number of characters transmitted. asnprintf returns the original str if there was enough room, otherwise it returns an allocated string.

If an error occurs, the result of printf, fprintf, snprintf, and asprintf is a negative value, and the result of asnprintf is NULL. No error returns occur for sprintf. For printf and fprintf, errno may be set according to fputc. For asprintf and asnprintf, errno may be set to ENOMEM if allocation fails, and for snprintf, errno may be set to EOVERFLOW if size or the output length exceeds INT_MAX.

Bugs
The “”’ (quote) flag does not work when locale’s thousands_sep is not empty.

Portability
ANSI C requires printf, fprintf, sprintf, and snprintf. asprintf and asnprintf are newlib extensions.

The ANSI C standard specifies that implementations must support at least formatted output of up to 509 characters. This implementation has no inherent limit.

Depending on how newlib was configured, not all format specifiers are supported.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.62 `sscanf`, `fscanf`, `scanf`—scan and format input

Synopsis

#include <stdio.h>

int scanf(const char *restrict format, ...);
int fscanf(FILE *restrict fd, const char *restrict format, ...);
int sscanf(const char *restrict str, const char *restrict format, ...);

int _scanf_r(struct _reent *ptr, const char *restrict format, ...);
int _fscanf_r(struct _reent *ptr, FILE *restrict fd, 
    const char *restrict format, ...);
int _sscanf_r(struct _reent *ptr, const char *restrict str,
    const char *restrict format, ...);

Description
scanf scans a series of input fields from standard input, one character at a time. Each field is interpreted according to a format specifier passed to scanf in the format string at *format. scanf stores the interpreted input from each field at the address passed to it as the corresponding argument following format. You must supply the same number of format specifiers and address arguments as there are input fields.

There must be sufficient address arguments for the given format specifiers; if not the results are unpredictable and likely disasterous. Excess address arguments are merely ignored.

scanf often produces unexpected results if the input diverges from an expected pattern. Since the combination of gets or fgets followed by sscanf is safe and easy, that is the preferred way to be certain that a program is synchronized with input at the end of a line.

fscanf and sscanf are identical to scanf, other than the source of input: fscanf reads from a file, and sscanf from a string.

The routines _scanf_r, _fscanf_r, and _sscanf_r are reentrant versions of scanf, fscanf, and sscanf that take an additional first argument pointing to a reentrancy structure.

The string at *format is a character sequence composed of zero or more directives. Directives are composed of one or more whitespace characters, non-whitespace characters, and format specifications.

Whitespace characters are blank ( ), tab (\t), or newline (\n). When scanf encounters a whitespace character in the format string it will read (but not store) all consecutive whitespace characters up to the next non-whitespace character in the input.

Non-whitespace characters are all other ASCII characters except the percent sign (%). When scanf encounters a non-whitespace character in the format string it will read, but not store a matching non-whitespace character.

Format specifications tell scanf to read and convert characters from the input field into specific types of values, and store then in the locations specified by the address arguments.

Trailing whitespace is left unread unless explicitly matched in the format string.

The format specifiers must begin with a percent sign (%) and have the following form:

       %[*][width][size]type

Each format specification begins with the percent character (%). The other fields are:

*

an optional marker; if present, it suppresses interpretation and assignment of this input field.

width

an optional maximum field width: a decimal integer, which controls the maximum number of characters that will be read before converting the current input field. If the input field has fewer than width characters, scanf reads all the characters in the field, and then proceeds with the next field and its format specification.

If a whitespace or a non-convertable character occurs before width character are read, the characters up to that character are read, converted, and stored. Then scanf proceeds to the next format specification.

size

h, j, l, L, t, and z are optional size characters which override the default way that scanf interprets the data type of the corresponding argument.

Modifier   Type(s)
   hh      d, i, o, u, x, n  convert input to char,
                             store in char object

   h       d, i, o, u, x, n  convert input to short,
                             store in short object

   h       D, I, O, U, X     no effect
           e, f, c, s, p

   j       d, i, o, u, x, n  convert input to intmax_t,
                             store in intmax_t object

   j       all others        no effect

   l       d, i, o, u, x, n  convert input to long,
                             store in long object

   l       e, f, g           convert input to double
                             store in a double object

   l       D, I, O, U, X     no effect
           c, s, p

   ll      d, i, o, u, x, n  convert to long long,
                             store in long long

   L       d, i, o, u, x, n  convert to long long,
                             store in long long

   L       e, f, g, E, G     convert to long double,
                             store in long double

   L       all others        no effect

   t       d, i, o, u, x, n  convert input to ptrdiff_t,
                             store in ptrdiff_t object

   t       all others        no effect

   z       d, i, o, u, x, n  convert input to size_t,
                             store in size_t object

   z       all others        no effect

type

A character to specify what kind of conversion scanf performs. Here is a table of the conversion characters:

%: No conversion is done; the percent character (%) is stored.
c: Scans one character. Corresponding arg: (char *arg).
s: Reads a character string into the array supplied. Corresponding arg: (char arg[]).
[pattern]: Reads a non-empty character string into memory starting at arg. This area must be large enough to accept the sequence and a terminating null character which will be added automatically. (pattern is discussed in the paragraph following this table). Corresponding arg: (char *arg).
d: Reads a decimal integer into the corresponding arg: (int *arg).
D: Reads a decimal integer into the corresponding arg: (long *arg).
o: Reads an octal integer into the corresponding arg: (int *arg).
O: Reads an octal integer into the corresponding arg: (long *arg).
u: Reads an unsigned decimal integer into the corresponding arg: (unsigned int *arg).
U: Reads an unsigned decimal integer into the corresponding arg: (unsigned long *arg).
x,X: Read a hexadecimal integer into the corresponding arg: (int *arg).
e, f, g: Read a floating-point number into the corresponding arg: (float *arg).
E, F, G: Read a floating-point number into the corresponding arg: (double *arg).
i: Reads a decimal, octal or hexadecimal integer into the corresponding arg: (int *arg).
I: Reads a decimal, octal or hexadecimal integer into the corresponding arg: (long *arg).
n: Stores the number of characters read in the corresponding arg: (int *arg).
p: Stores a scanned pointer. ANSI C leaves the details to each implementation; this implementation treats %p exactly the same as %U. Corresponding arg: (void **arg).

A pattern of characters surrounded by square brackets can be used instead of the s type character. pattern is a set of characters which define a search set of possible characters making up the scanf input field. If the first character in the brackets is a caret (^), the search set is inverted to include all ASCII characters except those between the brackets. There is also a range facility which you can use as a shortcut. %[0-9] matches all decimal digits. The hyphen must not be the first or last character in the set. The character prior to the hyphen must be lexically less than the character after it.

Here are some pattern examples:

%[abcd]: matches strings containing only a, b, c, and d.
%[^abcd]: matches strings containing any characters except a, b, c, or d
%[A-DW-Z]: matches strings containing A, B, C, D, W, X, Y, Z
%[z-a]: matches the characters z, -, and a

Floating point numbers (for field types e, f, g, E, F, G) must correspond to the following general form:

		[+/-] ddddd[.]ddd [E|e[+|-]ddd]

where objects inclosed in square brackets are optional, and ddd represents decimal, octal, or hexadecimal digits.

Returns
scanf returns the number of input fields successfully scanned, converted and stored; the return value does not include scanned fields which were not stored.

If scanf attempts to read at end-of-file, the return value is EOF.

If no fields were stored, the return value is 0.

scanf might stop scanning a particular field before reaching the normal field end character, or may terminate entirely.

scanf stops scanning and storing the current field and moves to the next input field (if any) in any of the following situations:

The assignment suppressing character (*) appears after the % in the format specification; the current input field is scanned but not stored.
width characters have been read (width is a width specification, a positive decimal integer).
The next character read cannot be converted under the the current format (for example, if a Z is read when the format is decimal).
The next character in the input field does not appear in the search set (or does appear in the inverted search set).

When scanf stops scanning the current input field for one of these reasons, the next character is considered unread and used as the first character of the following input field, or the first character in a subsequent read operation on the input.

scanf will terminate under the following circumstances:

The next character in the input field conflicts with a corresponding non-whitespace character in the format string.
The next character in the input field is EOF.
The format string has been exhausted.

When the format string contains a character sequence that is not part of a format specification, the same character sequence must appear in the input; scanf will scan but not store the matched characters. If a conflict occurs, the first conflicting character remains in the input as if it had never been read.

Portability
scanf is ANSI C.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.63 `stdio_ext`,`fbufsize`,`fpending`,`flbf`,`freadable`,`fwritable`,`freading`,`__fwriting`—access internals of FILE structure

Synopsis

#include <stdio.h>
#include <stdio_ext.h>
size_t __fbufsize(FILE *fp);
size_t __fpending(FILE *fp);
int __flbf(FILE *fp);
int __freadable(FILE *fp);
int __fwritable(FILE *fp);
int __freading(FILE *fp);
int __fwriting(FILE *fp);

Description
These functions provides access to the internals of the FILE structure fp.

Returns
__fbufsize returns the number of bytes in the buffer of stream fp.

__fpending returns the number of bytes in the output buffer of stream fp.

__flbf returns nonzero if stream fp is line-buffered, and 0 if not.

__freadable returns nonzero if stream fp may be read, and 0 if not.

__fwritable returns nonzero if stream fp may be written, and 0 if not.

__freading returns nonzero if stream fp if the last operation on it was a read, or if it read-only, and 0 if not.

__fwriting returns nonzero if stream fp if the last operation on it was a write, or if it write-only, and 0 if not.

Portability
These functions originate from Solaris and are also provided by GNU libc.

No supporting OS subroutines are required.

4.64 `swprintf`, `fwprintf`, `wprintf`—wide character format output

Synopsis

#include <wchar.h>

int wprintf(const wchar_t *format, ...);
int fwprintf(FILE *__restrict fd,
    const wchar_t *__restrict format, ...);
int swprintf(wchar_t *__restrict str, size_t size,
    const wchar_t *__restrict format, ...);

int _wprintf_r(struct _reent *ptr, const wchar_t *format, ...);
int _fwprintf_r(struct _reent *ptr, FILE *fd,
    const wchar_t *format, ...);
int _swprintf_r(struct _reent *ptr, wchar_t *str,
    size_t size, const wchar_t *format, ...);

Description
wprintf accepts a series of arguments, applies to each a format specifier from *format, and writes the formatted data to stdout, without a terminating NUL wide character. The behavior of wprintf is undefined if there are not enough arguments for the format or if any argument is not the right type for the corresponding conversion specifier. wprintf returns when it reaches the end of the format string. If there are more arguments than the format requires, excess arguments are ignored.

fwprintf is like wprintf, except that output is directed to the stream fd rather than stdout.

swprintf is like wprintf, except that output is directed to the buffer str with a terminating wide NUL, and the resulting string length is limited to at most size wide characters, including the terminating NUL. It is considered an error if the output (including the terminating wide-NULL) does not fit into size wide characters. (This error behavior is not the same as for snprintf, which swprintf is otherwise completely analogous to. While snprintf allows the needed size to be known simply by giving size=0, swprintf does not, giving an error instead.)

For swprintf the behavior is undefined if the output *str overlaps with one of the arguments. Behavior is also undefined if the argument for %n within *format overlaps another argument.

format is a pointer to a wide character string containing two types of objects: ordinary characters (other than %), which are copied unchanged to the output, and conversion specifications, each of which is introduced by %. (To include % in the output, use %% in the format string.) A conversion specification has the following form:

       %[pos][flags][width][.prec][size]type

The fields of the conversion specification have the following meanings:

pos
Conversions normally consume arguments in the order that they are presented. However, it is possible to consume arguments out of order, and reuse an argument for more than one conversion specification (although the behavior is undefined if the same argument is requested with different types), by specifying pos, which is a decimal integer followed by ’$’. The integer must be between 1 and <NL_ARGMAX> from limits.h, and if argument %n$ is requested, all earlier arguments must be requested somewhere within format. If positional parameters are used, then all conversion specifications except for %% must specify a position. This positional parameters method is a POSIX extension to the C standard definition for the functions.
flags
flags is an optional sequence of characters which control output justification, numeric signs, decimal points, trailing zeros, and octal and hex prefixes. The flag characters are minus (-), plus (+), space ( ), zero (0), sharp (#), and quote ('). They can appear in any combination, although not all flags can be used for all conversion specification types.

'

A POSIX extension to the C standard. However, this implementation presently treats it as a no-op, which is the default behavior for the C locale, anyway. (If it did what it is supposed to, when type were i, d, u, f, F, g, or G, the integer portion of the conversion would be formatted with thousands’ grouping wide characters.)

-

The result of the conversion is left justified, and the right is padded with blanks. If you do not use this flag, the result is right justified, and padded on the left.

+

The result of a signed conversion (as determined by type of d, i, a, A, e, E, f, F, g, or G) will always begin with a plus or minus sign. (If you do not use this flag, positive values do not begin with a plus sign.)

" " (space)

If the first character of a signed conversion specification is not a sign, or if a signed conversion results in no characters, the result will begin with a space. If the space ( ) flag and the plus (+) flag both appear, the space flag is ignored.

0

If the type character is d, i, o, u, x, X, a, A, e, E, f, F, g, or G: leading zeros are used to pad the field width (following any indication of sign or base); no spaces are used for padding. If the zero (0) and minus (-) flags both appear, the zero (0) flag will be ignored. For d, i, o, u, x, and X conversions, if a precision prec is specified, the zero (0) flag is ignored.

Note that 0 is interpreted as a flag, not as the beginning of a field width.

#

The result is to be converted to an alternative form, according to the type character:

o

Increases precision to force the first digit of the result to be a zero.

x

A non-zero result will have a 0x prefix.

X

A non-zero result will have a 0X prefix.

a, A, e, E, f, or F

The result will always contain a decimal point even if no digits follow the point. (Normally, a decimal point appears only if a digit follows it.) Trailing zeros are removed.

g or G

The result will always contain a decimal point even if no digits follow the point. Trailing zeros are not removed.

all others

Undefined.
width
width is an optional minimum field width. You can either specify it directly as a decimal integer, or indirectly by using instead an asterisk (*), in which case an int argument is used as the field width. If positional arguments are used, then the width must also be specified positionally as *m$, with m as a decimal integer. Negative field widths are treated as specifying the minus (-) flag for left justfication, along with a positive field width. The resulting format may be wider than the specified width.
prec
prec is an optional field; if present, it is introduced with ‘.’ (a period). You can specify the precision either directly as a decimal integer or indirectly by using an asterisk (*), in which case an int argument is used as the precision. If positional arguments are used, then the precision must also be specified positionally as *m$, with m as a decimal integer. Supplying a negative precision is equivalent to omitting the precision. If only a period is specified the precision is zero. The effect depends on the conversion type.

d, i, o, u, x, or X

Minimum number of digits to appear. If no precision is given, defaults to 1.

a or A

Number of digits to appear after the decimal point. If no precision is given, the precision defaults to the minimum needed for an exact representation.

e, E, f or F

Number of digits to appear after the decimal point. If no precision is given, the precision defaults to 6.

g or G

Maximum number of significant digits. A precision of 0 is treated the same as a precision of 1. If no precision is given, the precision defaults to 6.

s or S

Maximum number of characters to print from the string. If no precision is given, the entire string is printed.

all others

undefined.
size
size is an optional modifier that changes the data type that the corresponding argument has. Behavior is unspecified if a size is given that does not match the type.

hh

With d, i, o, u, x, or X, specifies that the argument should be converted to a signed char or unsigned char before printing.

With n, specifies that the argument is a pointer to a signed char.

h

With d, i, o, u, x, or X, specifies that the argument should be converted to a short or unsigned short before printing.

With n, specifies that the argument is a pointer to a short.

l

With d, i, o, u, x, or X, specifies that the argument is a long or unsigned long.

With c, specifies that the argument has type wint_t.

With s, specifies that the argument is a pointer to wchar_t.

With n, specifies that the argument is a pointer to a long.

With a, A, e, E, f, F, g, or G, has no effect (because of vararg promotion rules, there is no need to distinguish between float and double).

ll

With d, i, o, u, x, or X, specifies that the argument is a long long or unsigned long long.

With n, specifies that the argument is a pointer to a long long.

j

With d, i, o, u, x, or X, specifies that the argument is an intmax_t or uintmax_t.

With n, specifies that the argument is a pointer to an intmax_t.

z

With d, i, o, u, x, or X, specifies that the argument is a size_t.

With n, specifies that the argument is a pointer to a size_t.

t

With d, i, o, u, x, or X, specifies that the argument is a ptrdiff_t.

With n, specifies that the argument is a pointer to a ptrdiff_t.

L

With a, A, e, E, f, F, g, or G, specifies that the argument is a long double.
type
type specifies what kind of conversion wprintf performs. Here is a table of these:

%

Prints the percent character (%).

c

If no l qualifier is present, the int argument shall be converted to a wide character as if by calling the btowc() function and the resulting wide character shall be written. Otherwise, the wint_t argument shall be converted to wchar_t, and written.

C

Short for %lc. A POSIX extension to the C standard.

s

If no l qualifier is present, the application shall ensure that the argument is a pointer to a character array containing a character sequence beginning in the initial shift state. Characters from the array shall be converted as if by repeated calls to the mbrtowc() function, with the conversion state described by an mbstate_t object initialized to zero before the first character is converted, and written up to (but not including) the terminating null wide character. If the precision is specified, no more than that many wide characters shall be written. If the precision is not specified, or is greater than the size of the array, the application shall ensure that the array contains a null wide character.

If an l qualifier is present, the application shall ensure that the argument is a pointer to an array of type wchar_t. Wide characters from the array shall be written up to (but not including) a terminating null wide character. If no precision is specified, or is greater than the size of the array, the application shall ensure that the array contains a null wide character. If a precision is specified, no more than that many wide characters shall be written.

S

Short for %ls. A POSIX extension to the C standard.

d or i

Prints a signed decimal integer; takes an int. Leading zeros are inserted as necessary to reach the precision. A value of 0 with a precision of 0 produces an empty string.

o

Prints an unsigned octal integer; takes an unsigned. Leading zeros are inserted as necessary to reach the precision. A value of 0 with a precision of 0 produces an empty string.

u

Prints an unsigned decimal integer; takes an unsigned. Leading zeros are inserted as necessary to reach the precision. A value of 0 with a precision of 0 produces an empty string.

x

Prints an unsigned hexadecimal integer (using abcdef as digits beyond 9); takes an unsigned. Leading zeros are inserted as necessary to reach the precision. A value of 0 with a precision of 0 produces an empty string.

X

Like x, but uses ABCDEF as digits beyond 9.

f

Prints a signed value of the form [-]9999.9999, with the precision determining how many digits follow the decimal point; takes a double (remember that float promotes to double as a vararg). The low order digit is rounded to even. If the precision results in at most DECIMAL_DIG digits, the result is rounded correctly; if more than DECIMAL_DIG digits are printed, the result is only guaranteed to round back to the original value.

If the value is infinite, the result is inf, and no zero padding is performed. If the value is not a number, the result is nan, and no zero padding is performed.

F

Like f, but uses INF and NAN for non-finite numbers.

e

Prints a signed value of the form [-]9.9999e[+|-]999; takes a double. The digit before the decimal point is non-zero if the value is non-zero. The precision determines how many digits appear between . and e, and the exponent always contains at least two digits. The value zero has an exponent of zero. If the value is not finite, it is printed like f.

E

Like e, but using E to introduce the exponent, and like F for non-finite values.

g

Prints a signed value in either f or e form, based on the given value and precision—an exponent less than -4 or greater than the precision selects the e form. Trailing zeros and the decimal point are printed only if necessary; takes a double.

G

Like g, except use F or E form.

a

Prints a signed value of the form [-]0x1.ffffp[+|-]9; takes a double. The letters abcdef are used for digits beyond 9. The precision determines how many digits appear after the decimal point. The exponent contains at least one digit, and is a decimal value representing the power of 2; a value of 0 has an exponent of 0. Non-finite values are printed like f.

A

Like a, except uses X, P, and ABCDEF instead of lower case.

n

Takes a pointer to int, and stores a count of the number of bytes written so far. No output is created.

p

Takes a pointer to void, and prints it in an implementation-defined format. This implementation is similar to %#tx), except that 0x appears even for the NULL pointer.

m

Prints the output of strerror(errno); no argument is required. A GNU extension.

_wprintf_r, _fwprintf_r, _swprintf_r, are simply reentrant versions of the functions above.

Returns
On success, swprintf return the number of wide characters in the output string, except the concluding NUL is not counted. wprintf and fwprintf return the number of characters transmitted.

If an error occurs, the result of wprintf, fwprintf, and swprintf is a negative value. For wprintf and fwprintf, errno may be set according to fputwc. For swprintf, errno may be set to EOVERFLOW if size is greater than INT_MAX / sizeof (wchar_t), or when the output does not fit into size wide characters (including the terminating wide NULL).

Bugs
The “”’ (quote) flag does not work when locale’s thousands_sep is not empty.

Portability
POSIX-1.2008 with extensions; C99 (compliant except for POSIX extensions).

Depending on how newlib was configured, not all format specifiers are supported.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.65 `swscanf`, `fwscanf`, `wscanf`—scan and format wide character input

Synopsis

#include <stdio.h>

int wscanf(const wchar_t *__restrict format, ...);
int fwscanf(FILE *__restrict fd,
    const wchar_t *__restrict format, ...);
int swscanf(const wchar_t *__restrict str, 
    const wchar_t *__restrict format, ...);

int _wscanf_r(struct _reent *ptr, const wchar_t *format, ...);
int _fwscanf_r(struct _reent *ptr, FILE *fd, 
    const wchar_t *format, ...);
int _swscanf_r(struct _reent *ptr, const wchar_t *str,
    const wchar_t *format, ...);

Description
wscanf scans a series of input fields from standard input, one wide character at a time. Each field is interpreted according to a format specifier passed to wscanf in the format string at *format. wscanf stores the interpreted input from each field at the address passed to it as the corresponding argument following format. You must supply the same number of format specifiers and address arguments as there are input fields.

There must be sufficient address arguments for the given format specifiers; if not the results are unpredictable and likely disasterous. Excess address arguments are merely ignored.

wscanf often produces unexpected results if the input diverges from an expected pattern. Since the combination of gets or fgets followed by swscanf is safe and easy, that is the preferred way to be certain that a program is synchronized with input at the end of a line.

fwscanf and swscanf are identical to wscanf, other than the source of input: fwscanf reads from a file, and swscanf from a string.

The routines _wscanf_r, _fwscanf_r, and _swscanf_r are reentrant versions of wscanf, fwscanf, and swscanf that take an additional first argument pointing to a reentrancy structure.

The string at *format is a wide character sequence composed of zero or more directives. Directives are composed of one or more whitespace characters, non-whitespace characters, and format specifications.

Whitespace characters are blank ( ), tab (\t), or newline (\n). When wscanf encounters a whitespace character in the format string it will read (but not store) all consecutive whitespace characters up to the next non-whitespace character in the input.

Non-whitespace characters are all other ASCII characters except the percent sign (%). When wscanf encounters a non-whitespace character in the format string it will read, but not store a matching non-whitespace character.

Format specifications tell wscanf to read and convert characters from the input field into specific types of values, and store then in the locations specified by the address arguments.

Trailing whitespace is left unread unless explicitly matched in the format string.

The format specifiers must begin with a percent sign (%) and have the following form:

       %[*][width][size]type

Each format specification begins with the percent character (%). The other fields are:

*

an optional marker; if present, it suppresses interpretation and assignment of this input field.

width

an optional maximum field width: a decimal integer, which controls the maximum number of characters that will be read before converting the current input field. If the input field has fewer than width characters, wscanf reads all the characters in the field, and then proceeds with the next field and its format specification.

If a whitespace or a non-convertable wide character occurs before width character are read, the characters up to that character are read, converted, and stored. Then wscanf proceeds to the next format specification.

size

h, j, l, L, t, and z are optional size characters which override the default way that wscanf interprets the data type of the corresponding argument.

Modifier   Type(s)
   hh      d, i, o, u, x, n  convert input to char,
                             store in char object

   h       d, i, o, u, x, n  convert input to short,
                             store in short object

   h       e, f, c, s, p     no effect

   j       d, i, o, u, x, n  convert input to intmax_t,
                             store in intmax_t object

   j       all others        no effect

   l       d, i, o, u, x, n  convert input to long,
                             store in long object

   l       e, f, g           convert input to double
                             store in a double object

   l       c, s, [           the input is stored in a wchar_t object

   l       p                 no effect

   ll      d, i, o, u, x, n  convert to long long,
                             store in long long

   L       d, i, o, u, x, n  convert to long long,
                             store in long long

   L       e, f, g, E, G     convert to long double,
                             store in long double

   L       all others        no effect

   t       d, i, o, u, x, n  convert input to ptrdiff_t,
                             store in ptrdiff_t object

   t       all others        no effect

   z       d, i, o, u, x, n  convert input to size_t,
                             store in size_t object

   z       all others        no effect

type

A character to specify what kind of conversion wscanf performs. Here is a table of the conversion characters:

%: No conversion is done; the percent character (%) is stored.
c: Scans one wide character. Corresponding arg: (char *arg). Otherwise, if an l specifier is present, the corresponding arg is a (wchar_t *arg).
s: Reads a character string into the array supplied. Corresponding arg: (char arg[]). If an l specifier is present, the corresponding arg is a (wchar_t *arg).
[pattern]: Reads a non-empty character string into memory starting at arg. This area must be large enough to accept the sequence and a terminating null character which will be added automatically. (pattern is discussed in the paragraph following this table). Corresponding arg: (char *arg). If an l specifier is present, the corresponding arg is a (wchar_t *arg).
d: Reads a decimal integer into the corresponding arg: (int *arg).
o: Reads an octal integer into the corresponding arg: (int *arg).
u: Reads an unsigned decimal integer into the corresponding arg: (unsigned int *arg).
x,X: Read a hexadecimal integer into the corresponding arg: (int *arg).
e, f, g: Read a floating-point number into the corresponding arg: (float *arg).
E, F, G: Read a floating-point number into the corresponding arg: (double *arg).
i: Reads a decimal, octal or hexadecimal integer into the corresponding arg: (int *arg).
n: Stores the number of characters read in the corresponding arg: (int *arg).
p: Stores a scanned pointer. ANSI C leaves the details to each implementation; this implementation treats %p exactly the same as %U. Corresponding arg: (void **arg).

A pattern of characters surrounded by square brackets can be used instead of the s type character. pattern is a set of characters which define a search set of possible characters making up the wscanf input field. If the first character in the brackets is a caret (^), the search set is inverted to include all ASCII characters except those between the brackets. There is no range facility as is defined in the corresponding non-wide character scanf functions. Ranges are not part of the POSIX standard.

Here are some pattern examples:

%[abcd]: matches wide character strings containing only a, b, c, and d.
%[^abcd]: matches wide character strings containing any characters except a, b, c, or d.
%[A-DW-Z]: Note: No wide character ranges, so this expression matches wide character strings containing A, -, D, W, Z.

Floating point numbers (for field types e, f, g, E, F, G) must correspond to the following general form:

		[+/-] ddddd[.]ddd [E|e[+|-]ddd]

where objects inclosed in square brackets are optional, and ddd represents decimal, octal, or hexadecimal digits.

Returns
wscanf returns the number of input fields successfully scanned, converted and stored; the return value does not include scanned fields which were not stored.

If wscanf attempts to read at end-of-file, the return value is EOF.

If no fields were stored, the return value is 0.

wscanf might stop scanning a particular field before reaching the normal field end character, or may terminate entirely.

wscanf stops scanning and storing the current field and moves to the next input field (if any) in any of the following situations:

The assignment suppressing character (*) appears after the % in the format specification; the current input field is scanned but not stored.
width characters have been read (width is a width specification, a positive decimal integer).
The next wide character read cannot be converted under the the current format (for example, if a Z is read when the format is decimal).
The next wide character in the input field does not appear in the search set (or does appear in the inverted search set).

When wscanf stops scanning the current input field for one of these reasons, the next character is considered unread and used as the first character of the following input field, or the first character in a subsequent read operation on the input.

wscanf will terminate under the following circumstances:

The next wide character in the input field conflicts with a corresponding non-whitespace character in the format string.
The next wide character in the input field is WEOF.
The format string has been exhausted.

When the format string contains a wide character sequence that is not part of a format specification, the same wide character sequence must appear in the input; wscanf will scan but not store the matched characters. If a conflict occurs, the first conflicting wide character remains in the input as if it had never been read.

Portability
wscanf is C99, POSIX-1.2008.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.66 `tmpfile`—create a temporary file

Synopsis

#include <stdio.h>
FILE *tmpfile(void);

FILE *_tmpfile_r(struct _reent *reent);

Description
Create a temporary file (a file which will be deleted automatically), using a name generated by tmpnam. The temporary file is opened with the mode "wb+", permitting you to read and write anywhere in it as a binary file (without any data transformations the host system may perform for text files).

The alternate function _tmpfile_r is a reentrant version. The argument reent is a pointer to a reentrancy structure.

Returns
tmpfile normally returns a pointer to the temporary file. If no temporary file could be created, the result is NULL, and errno records the reason for failure.

Portability
Both ANSI C and the System V Interface Definition (Issue 2) require tmpfile.

Supporting OS subroutines required: close, fstat, getpid, isatty, lseek, open, read, sbrk, write.

tmpfile also requires the global pointer environ.

4.67 `tmpnam`, `tempnam`—name for a temporary file

Synopsis

#include <stdio.h>
char *tmpnam(char *s);
char *tempnam(char *dir, char *pfx);
char *_tmpnam_r(struct _reent *reent, char *s);
char *_tempnam_r(struct _reent *reent, char *dir, char *pfx);

Description
Use either of these functions to generate a name for a temporary file. The generated name is guaranteed to avoid collision with other files (for up to TMP_MAX calls of either function).

tmpnam generates file names with the value of P_tmpdir (defined in ‘stdio.h’) as the leading directory component of the path.

You can use the tmpnam argument s to specify a suitable area of memory for the generated filename; otherwise, you can call tmpnam(NULL) to use an internal static buffer.

tempnam allows you more control over the generated filename: you can use the argument dir to specify the path to a directory for temporary files, and you can use the argument pfx to specify a prefix for the base filename.

If dir is NULL, tempnam will attempt to use the value of environment variable TMPDIR instead; if there is no such value, tempnam uses the value of P_tmpdir (defined in ‘stdio.h’).

If you don’t need any particular prefix to the basename of temporary files, you can pass NULL as the pfx argument to tempnam.

_tmpnam_r and _tempnam_r are reentrant versions of tmpnam and tempnam respectively. The extra argument reent is a pointer to a reentrancy structure.

Warnings
The generated filenames are suitable for temporary files, but do not in themselves make files temporary. Files with these names must still be explicitly removed when you no longer want them.

If you supply your own data area s for tmpnam, you must ensure that it has room for at least L_tmpnam elements of type char.

Returns
Both tmpnam and tempnam return a pointer to the newly generated filename.

Portability
ANSI C requires tmpnam, but does not specify the use of P_tmpdir. The System V Interface Definition (Issue 2) requires both tmpnam and tempnam.

Supporting OS subroutines required: close, fstat, getpid, isatty, lseek, open, read, sbrk, write.

The global pointer environ is also required.

4.68 `ungetc`—push data back into a stream

Synopsis

#include <stdio.h>
int ungetc(int c, FILE *stream);

int _ungetc_r(struct _reent *reent, int c, FILE *stream);

Description
ungetc is used to return bytes back to stream to be read again. If c is EOF, the stream is unchanged. Otherwise, the unsigned char c is put back on the stream, and subsequent reads will see the bytes pushed back in reverse order. Pushed byes are lost if the stream is repositioned, such as by fseek, fsetpos, or rewind.

The underlying file is not changed, but it is possible to push back something different than what was originally read. Ungetting a character will clear the end-of-stream marker, and decrement the file position indicator. Pushing back beyond the beginning of a file gives unspecified behavior.

The alternate function _ungetc_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
The character pushed back, or EOF on error.

Portability
ANSI C requires ungetc, but only requires a pushback buffer of one byte; although this implementation can handle multiple bytes, not all can. Pushing back a signed char is a common application bug.

Supporting OS subroutines required: sbrk.

4.69 `ungetwc`—push wide character data back into a stream

Synopsis

#include <stdio.h>
#include <wchar.h>
wint_t ungetwc(wint_t wc, FILE *stream);

wint_t _ungetwc_r(struct _reent *reent, wint_t wc, FILE *stream);

Description
ungetwc is used to return wide characters back to stream to be read again. If wc is WEOF, the stream is unchanged. Otherwise, the wide character wc is put back on the stream, and subsequent reads will see the wide chars pushed back in reverse order. Pushed wide chars are lost if the stream is repositioned, such as by fseek, fsetpos, or rewind.

The alternate function _ungetwc_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
The wide character pushed back, or WEOF on error.

Portability
C99

4.70 `vfprintf`, `vprintf`, `vsprintf`, `vsnprintf`, `vasprintf`, `vasnprintf`—format argument list

Synopsis

#include <stdio.h>
#include <stdarg.h>
int vprintf(const char *fmt, va_list list);
int vfprintf(FILE *fp, const char *fmt, va_list list);
int vsprintf(char *str, const char *fmt, va_list list);
int vsnprintf(char *str, size_t size, const char *fmt,
    va_list list);
int vasprintf(char **strp, const char *fmt, va_list list);
char *vasnprintf(char *str, size_t *size, const char *fmt,
    va_list list);

int _vprintf_r(struct _reent *reent, const char *fmt,
    va_list list);
int _vfprintf_r(struct _reent *reent, FILE *fp,
    const char *fmt, va_list list);
int _vsprintf_r(struct _reent *reent, char *str,
    const char *fmt, va_list list);
int _vasprintf_r(struct _reent *reent, char **str,
    const char *fmt, va_list list);
int _vsnprintf_r(struct _reent *reent, char *str,
    size_t size, const char *fmt, va_list list);
char *_vasnprintf_r(struct _reent *reent, char *str,
    size_t *size, const char *fmt, va_list list);

Description
vprintf, vfprintf, vasprintf, vsprintf, vsnprintf, and vasnprintf are (respectively) variants of printf, fprintf, asprintf, sprintf, snprintf, and asnprintf. They differ only in allowing their caller to pass the variable argument list as a va_list object (initialized by va_start) rather than directly accepting a variable number of arguments. The caller is responsible for calling va_end.

_vprintf_r, _vfprintf_r, _vasprintf_r, _vsprintf_r, _vsnprintf_r, and _vasnprintf_r are reentrant versions of the above.

Returns
The return values are consistent with the corresponding functions.

Portability
ANSI C requires vprintf, vfprintf, vsprintf, and vsnprintf. The remaining functions are newlib extensions.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.71 `vfscanf`, `vscanf`, `vsscanf`—format argument list

Synopsis

#include <stdio.h>
#include <stdarg.h>
int vscanf(const char *fmt, va_list list);
int vfscanf(FILE *fp, const char *fmt, va_list list);
int vsscanf(const char *str, const char *fmt, va_list list);

int _vscanf_r(struct _reent *reent, const char *fmt,
    va_list list);
int _vfscanf_r(struct _reent *reent, FILE *fp, const char *fmt,
    va_list list);
int _vsscanf_r(struct _reent *reent, const char *str,
    const char *fmt, va_list list);

Description
vscanf, vfscanf, and vsscanf are (respectively) variants of scanf, fscanf, and sscanf. They differ only in allowing their caller to pass the variable argument list as a va_list object (initialized by va_start) rather than directly accepting a variable number of arguments.

Returns
The return values are consistent with the corresponding functions: vscanf returns the number of input fields successfully scanned, converted, and stored; the return value does not include scanned fields which were not stored.

If vscanf attempts to read at end-of-file, the return value is EOF.

If no fields were stored, the return value is 0.

The routines _vscanf_r, _vfscanf_f, and _vsscanf_r are reentrant versions which take an additional first parameter which points to the reentrancy structure.

Portability
These are GNU extensions.

Supporting OS subroutines required:

4.72 `vfwprintf`, `vwprintf`, `vswprintf`—wide character format argument list

Synopsis

#include <stdio.h>
#include <stdarg.h>
#include <wchar.h>
int vwprintf(const wchar_t *__restrict fmt, va_list list);
int vfwprintf(FILE *__restrict fp,
    const wchar_t *__restrict fmt, va_list list);
int vswprintf(wchar_t * __restrict str, size_t size,
    const wchar_t *__ restrict fmt, va_list list);

int _vwprintf_r(struct _reent *reent, const wchar_t *fmt,
    va_list list);
int _vfwprintf_r(struct _reent *reent, FILE *fp,
    const wchar_t *fmt, va_list list);
int _vswprintf_r(struct _reent *reent, wchar_t *str,
    size_t size, const wchar_t *fmt, va_list list);

Description
vwprintf, vfwprintf and vswprintf are (respectively) variants of wprintf, fwprintf and swprintf. They differ only in allowing their caller to pass the variable argument list as a va_list object (initialized by va_start) rather than directly accepting a variable number of arguments. The caller is responsible for calling va_end.

_vwprintf_r, _vfwprintf_r and _vswprintf_r are reentrant versions of the above.

Returns
The return values are consistent with the corresponding functions.

Portability
POSIX-1.2008 with extensions; C99 (compliant except for POSIX extensions).

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

See Also
wprintf, fwprintf and swprintf.

4.73 `vfwscanf`, `vwscanf`, `vswscanf`—scan and format argument list from wide character input

Synopsis

#include <stdio.h>
#include <stdarg.h>
int vwscanf(const wchar_t *__restrict fmt, va_list list);
int vfwscanf(FILE *__restrict fp,
    const wchar_t *__restrict fmt, va_list list);
int vswscanf(const wchar_t *__restrict str,
    const wchar_t *__restrict fmt, va_list list);

int _vwscanf(struct _reent *reent, const wchar_t *fmt,
    va_list list);
int _vfwscanf(struct _reent *reent, FILE *fp,
    const wchar_t *fmt, va_list list);
int _vswscanf(struct _reent *reent, const wchar_t *str,
    const wchar_t *fmt, va_list list);

Description
vwscanf, vfwscanf, and vswscanf are (respectively) variants of wscanf, fwscanf, and swscanf. They differ only in allowing their caller to pass the variable argument list as a va_list object (initialized by va_start) rather than directly accepting a variable number of arguments.

Returns
The return values are consistent with the corresponding functions: vwscanf returns the number of input fields successfully scanned, converted, and stored; the return value does not include scanned fields which were not stored.

If vwscanf attempts to read at end-of-file, the return value is EOF.

If no fields were stored, the return value is 0.

The routines _vwscanf, _vfwscanf, and _vswscanf are reentrant versions which take an additional first parameter which points to the reentrancy structure.

Portability
C99, POSIX-1.2008

4.74 `viprintf`, `vfiprintf`, `vsiprintf`, `vsniprintf`, `vasiprintf`, `vasniprintf`—format argument list (integer only)

Synopsis

#include <stdio.h>
#include <stdarg.h>
int viprintf(const char *fmt, va_list list);
int vfiprintf(FILE *fp, const char *fmt, va_list list);
int vsiprintf(char *str, const char *fmt, va_list list);
int vsniprintf(char *str, size_t size, const char *fmt,
    va_list list);
int vasiprintf(char **strp, const char *fmt, va_list list);
char *vasniprintf(char *str, size_t *size, const char *fmt,
    va_list list);

int _viprintf_r(struct _reent *reent, const char *fmt,
    va_list list);
int _vfiprintf_r(struct _reent *reent, FILE *fp,
    const char *fmt, va_list list);
int _vsiprintf_r(struct _reent *reent, char *str,
    const char *fmt, va_list list);
int _vsniprintf_r(struct _reent *reent, char *str,
    size_t size, const char *fmt, va_list list);
int _vasiprintf_r(struct _reent *reent, char **str,
    const char *fmt, va_list list);
char *_vasniprintf_r(struct _reent *reent, char *str,
    size_t *size, const char *fmt, va_list list);

Description
viprintf, vfiprintf, vasiprintf, vsiprintf, vsniprintf, and vasniprintf are (respectively) variants of iprintf, fiprintf, asiprintf, siprintf, sniprintf, and asniprintf. They differ only in allowing their caller to pass the variable argument list as a va_list object (initialized by va_start) rather than directly accepting a variable number of arguments. The caller is responsible for calling va_end.

_viprintf_r, _vfiprintf_r, _vasiprintf_r, _vsiprintf_r, _vsniprintf_r, and _vasniprintf_r are reentrant versions of the above.

Returns
The return values are consistent with the corresponding functions:

Portability
All of these functions are newlib extensions.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

4.75 `viscanf`, `vfiscanf`, `vsiscanf`—format argument list

Synopsis

#include <stdio.h>
#include <stdarg.h>
int viscanf(const char *fmt, va_list list);
int vfiscanf(FILE *fp, const char *fmt, va_list list);
int vsiscanf(const char *str, const char *fmt, va_list list);

int _viscanf_r(struct _reent *reent, const char *fmt, 
    va_list list);
int _vfiscanf_r(struct _reent *reent, FILE *fp, const char *fmt, 
    va_list list);
int _vsiscanf_r(struct _reent *reent, const char *str,
    const char *fmt, va_list list);

Description
viscanf, vfiscanf, and vsiscanf are (respectively) variants of iscanf, fiscanf, and siscanf. They differ only in allowing their caller to pass the variable argument list as a va_list object (initialized by va_start) rather than directly accepting a variable number of arguments.

Returns
The return values are consistent with the corresponding functions: viscanf returns the number of input fields successfully scanned, converted, and stored; the return value does not include scanned fields which were not stored.

If viscanf attempts to read at end-of-file, the return value is EOF.

If no fields were stored, the return value is 0.

The routines _viscanf_r, _vfiscanf_f, and _vsiscanf_r are reentrant versions which take an additional first parameter which points to the reentrancy structure.

Portability
These are newlib extensions.

Supporting OS subroutines required:

5 Strings and Memory (`string.h`)

This chapter describes string-handling functions and functions for managing areas of memory. The corresponding declarations are in string.h.

• bcmp:		Compare two memory areas
• bcopy:		Copy memory regions
• bzero:		Initialize memory to zero
• index:		Search for character in string
• memccpy:		Copy memory regions up to end-token
• memchr:		Find character in memory
• memcmp:		Compare two memory areas
• memcpy:		Copy memory regions
• memmem:		Find memory segment
• memmove:		Move possibly overlapping memory
• mempcpy:		Copy memory regions and locate end
• memset:		Set an area of memory
• rindex:		Reverse search for character in string
• stpcpy:		Copy string returning a pointer to its end
• stpncpy:		Counted copy string returning a pointer to its end
• strcasecmp:		Compare strings ignoring case
• strcasestr:		Find string segment ignoring case
• strcat:		Concatenate strings
• strchr:		Search for character in string
• strcmp:		Character string compare
• strcoll:		Locale-specific character string compare
• strcpy:		Copy string
• strcspn:		Count chars not in string
• strerror:		Convert error number to string
• strerror_r:		Convert error number to string
• strlen:		Character string length
• strlwr:		Convert string to lowercase
• strncasecmp:		Compare strings ignoring case
• strncat:		Concatenate strings
• strncmp:		Character string compare
• strncpy:		Counted copy string
• strnlen:		Character string length
• strpbrk:		Find chars in string
• strrchr:		Reverse search for character in string
• strsignal:		Return signal message string
• strspn:		Find initial match
• strstr:		Find string segment
• strtok:		Get next token from a string
• strupr:		Convert string to upper case
• strxfrm:		Transform string
• swab:		Swap adjacent bytes
• wcscasecmp:		Compare wide character strings ignoring case
• wcsdup:		Wide character string duplicate
• wcsncasecmp:		Compare wide character strings ignoring case

5.1 `bcmp`—compare two memory areas

Synopsis

#include <strings.h>
int bcmp(const void *s1, const void *s2, size_t n);

Description
This function compares not more than n bytes of the object pointed to by s1 with the object pointed to by s2.

This function is identical to memcmp.

Returns
The function returns an integer greater than, equal to or less than zero according to whether the object pointed to by s1 is greater than, equal to or less than the object pointed to by s2.

Portability
bcmp requires no supporting OS subroutines.

5.2 `bcopy`—copy memory regions

Synopsis

#include <strings.h>
void bcopy(const void *in, void *out, size_t n);

Description
This function copies n bytes from the memory region pointed to by in to the memory region pointed to by out.

This function is implemented in term of memmove.

Portability
bcopy requires no supporting OS subroutines.

5.3 `bzero`—initialize memory to zero

Synopsis

#include <strings.h>
void bzero(void *b, size_t length);

Description
bzero initializes length bytes of memory, starting at address b, to zero.

Returns
bzero does not return a result.

Portability
bzero is in the Berkeley Software Distribution. Neither ANSI C nor the System V Interface Definition (Issue 2) require bzero.

bzero requires no supporting OS subroutines.

5.4 `index`—search for character in string

Synopsis

#include <strings.h>
char * index(const char *string, int c);

Description
This function finds the first occurence of c (converted to a char) in the string pointed to by string (including the terminating null character).

This function is identical to strchr.

Returns
Returns a pointer to the located character, or a null pointer if c does not occur in string.

Portability
index requires no supporting OS subroutines.

5.5 `memccpy`—copy memory regions with end-token check

Synopsis

#include <string.h>
void* memccpy(void *restrict out, const void *restrict in, 
    int endchar, size_t n);

Description
This function copies up to n bytes from the memory region pointed to by in to the memory region pointed to by out. If a byte matching the endchar is encountered, the byte is copied and copying stops.

If the regions overlap, the behavior is undefined.

Returns
memccpy returns a pointer to the first byte following the endchar in the out region. If no byte matching endchar was copied, then NULL is returned.

Portability
memccpy is a GNU extension.

memccpy requires no supporting OS subroutines.

5.6 `memchr`—find character in memory

Synopsis

#include <string.h>
void *memchr(const void *src, int c, size_t length);

Description
This function searches memory starting at *src for the character c. The search only ends with the first occurrence of c, or after length characters; in particular, NUL does not terminate the search.

Returns
If the character c is found within length characters of *src, a pointer to the character is returned. If c is not found, then NULL is returned.

Portability
memchr is ANSI C.

memchr requires no supporting OS subroutines.

5.7 `memcmp`—compare two memory areas

Synopsis

#include <string.h>
int memcmp(const void *s1, const void *s2, size_t n);

Description
This function compares not more than n characters of the object pointed to by s1 with the object pointed to by s2.

Portability
memcmp is ANSI C.

memcmp requires no supporting OS subroutines.

5.8 `memcpy`—copy memory regions

Synopsis

#include <string.h>
void* memcpy(void *restrict out, const void *restrict in,
    size_t n);

Description
This function copies n bytes from the memory region pointed to by in to the memory region pointed to by out.

If the regions overlap, the behavior is undefined.

Returns
memcpy returns a pointer to the first byte of the out region.

Portability
memcpy is ANSI C.

memcpy requires no supporting OS subroutines.

5.9 `memmem`—find memory segment

Synopsis

#include <string.h>
char *memmem(const void *s1, size_t l1, const void *s2,
    size_t l2);

Description

Locates the first occurrence in the memory region pointed to by s1 with length l1 of the sequence of bytes pointed to by s2 of length l2. If you already know the lengths of your haystack and needle, memmem can be much faster than strstr.

Returns
Returns a pointer to the located segment, or a null pointer if s2 is not found. If l2 is 0, s1 is returned.

Portability
memmem is a newlib extension.

memmem requires no supporting OS subroutines.

5.10 `memmove`—move possibly overlapping memory

Synopsis

#include <string.h>
void *memmove(void *dst, const void *src, size_t length);

Description
This function moves length characters from the block of memory starting at *src to the memory starting at *dst. memmove reproduces the characters correctly at *dst even if the two areas overlap.

Returns
The function returns dst as passed.

Portability
memmove is ANSI C.

memmove requires no supporting OS subroutines.

5.11 `mempcpy`—copy memory regions and return end pointer

Synopsis

#include <string.h>
void* mempcpy(void *out, const void *in, size_t n);

Description
This function copies n bytes from the memory region pointed to by in to the memory region pointed to by out.

If the regions overlap, the behavior is undefined.

Returns
mempcpy returns a pointer to the byte following the last byte copied to the out region.

Portability
mempcpy is a GNU extension.

mempcpy requires no supporting OS subroutines.

5.12 `memset`—set an area of memory

Synopsis

#include <string.h>
void *memset(void *dst, int c, size_t length);

Description
This function converts the argument c into an unsigned char and fills the first length characters of the array pointed to by dst to the value.

Returns
memset returns the value of dst.

Portability
memset is ANSI C.

memset requires no supporting OS subroutines.

5.13 `rindex`—reverse search for character in string

Synopsis

#include <string.h>
char * rindex(const char *string, int c);

Description
This function finds the last occurence of c (converted to a char) in the string pointed to by string (including the terminating null character).

This function is identical to strrchr.

Returns
Returns a pointer to the located character, or a null pointer if c does not occur in string.

Portability
rindex requires no supporting OS subroutines.

5.14 `stpcpy`—copy string returning a pointer to its end

Synopsis

#include <string.h>
char *stpcpy(char *restrict dst, const char *restrict src);

Description
stpcpy copies the string pointed to by src (including the terminating null character) to the array pointed to by dst.

Returns
This function returns a pointer to the end of the destination string, thus pointing to the trailing ’\0’.

Portability
stpcpy is a GNU extension, candidate for inclusion into POSIX/SUSv4.

stpcpy requires no supporting OS subroutines.

5.15 `stpncpy`—counted copy string returning a pointer to its end

Synopsis

#include <string.h>
char *stpncpy(char *restrict dst, const char *restrict src,
    size_t length);

Description
stpncpy copies not more than length characters from the the string pointed to by src (including the terminating null character) to the array pointed to by dst. If the string pointed to by src is shorter than length characters, null characters are appended to the destination array until a total of length characters have been written.

Returns
This function returns a pointer to the end of the destination string, thus pointing to the trailing ’\0’, or, if the destination string is not null-terminated, pointing to dst + n.

Portability
stpncpy is a GNU extension, candidate for inclusion into POSIX/SUSv4.

stpncpy requires no supporting OS subroutines.

5.16 `strcasecmp`—case-insensitive character string compare

Synopsis

#include <strings.h>
int strcasecmp(const char *a, const char *b);

Description
strcasecmp compares the string at a to the string at b in a case-insensitive manner.

Returns

If *a sorts lexicographically after *b (after both are converted to lowercase), strcasecmp returns a number greater than zero. If the two strings match, strcasecmp returns zero. If *a sorts lexicographically before *b, strcasecmp returns a number less than zero.

Portability
strcasecmp is in the Berkeley Software Distribution.

strcasecmp requires no supporting OS subroutines. It uses tolower() from elsewhere in this library.

5.17 `strcasestr`—case-insensitive character string search

Synopsis

#include <string.h>
char *strcasestr(const char *s, const char *find);

Description
strcasestr searchs the string s for the first occurrence of the sequence find. strcasestr is identical to strstr except the search is case-insensitive.

Returns

A pointer to the first case-insensitive occurrence of the sequence find or NULL if no match was found.

Portability
strcasestr is in the Berkeley Software Distribution.

strcasestr requires no supporting OS subroutines. It uses tolower() from elsewhere in this library.

5.18 `strcat`—concatenate strings

Synopsis

#include <string.h>
char *strcat(char *restrict dst, const char *restrict src);

Description
strcat appends a copy of the string pointed to by src (including the terminating null character) to the end of the string pointed to by dst. The initial character of src overwrites the null character at the end of dst.

Returns
This function returns the initial value of dst

Portability
strcat is ANSI C.

strcat requires no supporting OS subroutines.

5.19 `strchr`—search for character in string

Synopsis

#include <string.h>
char * strchr(const char *string, int c);

Description
This function finds the first occurence of c (converted to a char) in the string pointed to by string (including the terminating null character).

Returns
Returns a pointer to the located character, or a null pointer if c does not occur in string.

Portability
strchr is ANSI C.

strchr requires no supporting OS subroutines.

5.20 `strcmp`—character string compare

Synopsis

#include <string.h>
int strcmp(const char *a, const char *b);

Description
strcmp compares the string at a to the string at b.

Returns
If *a sorts lexicographically after *b, strcmp returns a number greater than zero. If the two strings match, strcmp returns zero. If *a sorts lexicographically before *b, strcmp returns a number less than zero.

Portability
strcmp is ANSI C.

strcmp requires no supporting OS subroutines.

5.21 `strcoll`—locale-specific character string compare

Synopsis

#include <string.h>
int strcoll(const char *stra, const char * strb);

Description
strcoll compares the string pointed to by stra to the string pointed to by strb, using an interpretation appropriate to the current LC_COLLATE state.

Returns
If the first string is greater than the second string, strcoll returns a number greater than zero. If the two strings are equivalent, strcoll returns zero. If the first string is less than the second string, strcoll returns a number less than zero.

Portability
strcoll is ANSI C.

strcoll requires no supporting OS subroutines.

5.22 `strcpy`—copy string

Synopsis

#include <string.h>
char *strcpy(char *dst, const char *src);

Description
strcpy copies the string pointed to by src (including the terminating null character) to the array pointed to by dst.

Returns
This function returns the initial value of dst.

Portability
strcpy is ANSI C.

strcpy requires no supporting OS subroutines.

5.23 `strcspn`—count characters not in string

Synopsis

size_t strcspn(const char *s1, const char *s2);

Description
This function computes the length of the initial part of the string pointed to by s1 which consists entirely of characters NOT from the string pointed to by s2 (excluding the terminating null character).

Returns
strcspn returns the length of the substring found.

Portability
strcspn is ANSI C.

strcspn requires no supporting OS subroutines.

5.24 `strerror`—convert error number to string

Synopsis

#include <string.h>
char *strerror(int errnum);
char *_strerror_r(struct _reent ptr, int errnum,
    int internal, int *error);

Description
strerror converts the error number errnum into a string. The value of errnum is usually a copy of errno. If errnum is not a known error number, the result points to an empty string.

This implementation of strerror prints out the following strings for each of the values defined in ‘errno.h’:

0: Success
E2BIG: Arg list too long
EACCES: Permission denied
EADDRINUSE: Address already in use
EADDRNOTAVAIL: Address not available
EADV: Advertise error
EAFNOSUPPORT: Address family not supported by protocol family
EAGAIN: No more processes
EALREADY: Socket already connected
EBADF: Bad file number
EBADMSG: Bad message
EBUSY: Device or resource busy
ECANCELED: Operation canceled
ECHILD: No children
ECOMM: Communication error
ECONNABORTED: Software caused connection abort
ECONNREFUSED: Connection refused
ECONNRESET: Connection reset by peer
EDEADLK: Deadlock
EDESTADDRREQ: Destination address required
EEXIST: File exists
EDOM: Mathematics argument out of domain of function
EFAULT: Bad address
EFBIG: File too large
EHOSTDOWN: Host is down
EHOSTUNREACH: Host is unreachable
EIDRM: Identifier removed
EILSEQ: Illegal byte sequence
EINPROGRESS: Connection already in progress
EINTR: Interrupted system call
EINVAL: Invalid argument
EIO: I/O error
EISCONN: Socket is already connected
EISDIR: Is a directory
ELIBACC: Cannot access a needed shared library
ELIBBAD: Accessing a corrupted shared library
ELIBEXEC: Cannot exec a shared library directly
ELIBMAX: Attempting to link in more shared libraries than system limit
ELIBSCN: .lib section in a.out corrupted
EMFILE: File descriptor value too large
EMLINK: Too many links
EMSGSIZE: Message too long
EMULTIHOP: Multihop attempted
ENAMETOOLONG: File or path name too long
ENETDOWN: Network interface is not configured
ENETRESET: Connection aborted by network
ENETUNREACH: Network is unreachable
ENFILE: Too many open files in system
ENOBUFS: No buffer space available
ENODATA: No data
ENODEV: No such device
ENOENT: No such file or directory
ENOEXEC: Exec format error
ENOLCK: No lock
ENOLINK: Virtual circuit is gone
ENOMEM: Not enough space
ENOMSG: No message of desired type
ENONET: Machine is not on the network
ENOPKG: No package
ENOPROTOOPT: Protocol not available
ENOSPC: No space left on device
ENOSR: No stream resources
ENOSTR: Not a stream
ENOSYS: Function not implemented
ENOTBLK: Block device required
ENOTCONN: Socket is not connected
ENOTDIR: Not a directory
ENOTEMPTY: Directory not empty
ENOTRECOVERABLE: State not recoverable
ENOTSOCK: Socket operation on non-socket
ENOTSUP: Not supported
ENOTTY: Not a character device
ENXIO: No such device or address
EOPNOTSUPP: Operation not supported on socket
EOVERFLOW: Value too large for defined data type
EOWNERDEAD: Previous owner died
EPERM: Not owner
EPIPE: Broken pipe
EPROTO: Protocol error
EPROTOTYPE: Protocol wrong type for socket
EPROTONOSUPPORT: Unknown protocol
ERANGE: Result too large
EREMOTE: Resource is remote
EROFS: Read-only file system
ESHUTDOWN: Can’t send after socket shutdown
ESOCKTNOSUPPORT: Socket type not supported
ESPIPE: Illegal seek
ESRCH: No such process
ESRMNT: Srmount error
ESTRPIPE: Strings pipe error
ETIME: Stream ioctl timeout
ETIMEDOUT: Connection timed out
ETXTBSY: Text file busy
EWOULDBLOCK: Operation would block (usually same as EAGAIN)
EXDEV: Cross-device link

_strerror_r is a reentrant version of the above.

Returns
This function returns a pointer to a string. Your application must not modify that string.

Portability
ANSI C requires strerror, but does not specify the strings used for each error number.

Although this implementation of strerror is reentrant (depending on _user_strerror), ANSI C declares that subsequent calls to strerror may overwrite the result string; therefore portable code cannot depend on the reentrancy of this subroutine.

Although this implementation of strerror guarantees a non-null result with a NUL-terminator, some implementations return NULL on failure. Although POSIX allows strerror to set errno to EINVAL on failure, this implementation does not do so (unless you provide _user_strerror).

POSIX recommends that unknown errnum result in a message including that value, however it is not a requirement and this implementation does not provide that information (unless you provide _user_strerror).

This implementation of strerror provides for user-defined extensibility. errno.h defines __ELASTERROR, which can be used as a base for user-defined error values. If the user supplies a routine named _user_strerror, and errnum passed to strerror does not match any of the supported values, _user_strerror is called with three arguments. The first is of type int, and is the errnum value unknown to strerror. The second is of type int, and matches the internal argument of _strerror_r; this should be zero if called from strerror and non-zero if called from any other function; _user_strerror can use this information to satisfy the POSIX rule that no other standardized function can overwrite a static buffer reused by strerror. The third is of type int *, and matches the error argument of _strerror_r; if a non-zero value is stored into that location (usually EINVAL), then strerror will set errno to that value, and the XPG variant of strerror_r will return that value instead of zero or ERANGE. _user_strerror returns a char * value; returning NULL implies that the user function did not choose to handle errnum. The default _user_strerror returns NULL for all input values. Note that _user_sterror must be thread-safe, and only denote errors via the third argument rather than modifying errno, if strerror and strerror_r are are to comply with POSIX.

strerror requires no supporting OS subroutines.

5.25 `strerror_r`—convert error number to string and copy to buffer

Synopsis

#include <string.h>
#ifdef _GNU_SOURCE
char *strerror_r(int errnum, char *buffer, size_t n);
#else
int strerror_r(int errnum, char *buffer, size_t n);
#endif

Description
strerror_r converts the error number errnum into a string and copies the result into the supplied buffer for a length up to n, including the NUL terminator. The value of errnum is usually a copy of errno. If errnum is not a known error number, the result is the empty string.

See strerror for how strings are mapped to errnum.

Returns
There are two variants: the GNU version always returns a NUL-terminated string, which is buffer if all went well, but which is another pointer if n was too small (leaving buffer untouched). If the return is not buffer, your application must not modify that string. The POSIX version returns 0 on success, EINVAL if errnum was not recognized, and ERANGE if n was too small. The variant chosen depends on macros that you define before inclusion of string.h.

Portability
strerror_r with a char * result is a GNU extension. strerror_r with an int result is required by POSIX 2001. This function is compliant only if _user_strerror is not provided, or if it is thread-safe and uses separate storage according to whether the second argument of that function is non-zero. For more details on _user_strerror, see the strerror documentation.

POSIX states that the contents of buf are unspecified on error, although this implementation guarantees a NUL-terminated string for all except n of 0.

POSIX recommends that unknown errnum result in a message including that value, however it is not a requirement and this implementation provides only an empty string (unless you provide _user_strerror). POSIX also recommends that unknown errnum fail with EINVAL even when providing such a message, however it is not a requirement and this implementation will return success if _user_strerror provided a non-empty alternate string without assigning into its third argument.

strerror_r requires no supporting OS subroutines.

5.26 `strlen`—character string length

Synopsis

#include <string.h>
size_t strlen(const char *str);

Description
The strlen function works out the length of the string starting at *str by counting chararacters until it reaches a NULL character.

Returns
strlen returns the character count.

Portability
strlen is ANSI C.

strlen requires no supporting OS subroutines.

5.27 `strlwr`—force string to lowercase

Synopsis

#include <string.h>
char *strlwr(char *a);

Description
strlwr converts each character in the string at a to lowercase.

Returns
strlwr returns its argument, a.

Portability
strlwr is not widely portable.

strlwr requires no supporting OS subroutines.

5.28 `strncasecmp`—case-insensitive character string compare

Synopsis

#include <strings.h>
int strncasecmp(const char *a, const char * b, size_t length);

Description
strncasecmp compares up to length characters from the string at a to the string at b in a case-insensitive manner.

Returns

If *a sorts lexicographically after *b (after both are converted to lowercase), strncasecmp returns a number greater than zero. If the two strings are equivalent, strncasecmp returns zero. If *a sorts lexicographically before *b, strncasecmp returns a number less than zero.

Portability
strncasecmp is in the Berkeley Software Distribution.

strncasecmp requires no supporting OS subroutines. It uses tolower() from elsewhere in this library.

5.29 `strncat`—concatenate strings

Synopsis

#include <string.h>
char *strncat(char *restrict dst, const char *restrict src,
    size_t length);

Description
strncat appends not more than length characters from the string pointed to by src (including the terminating null character) to the end of the string pointed to by dst. The initial character of src overwrites the null character at the end of dst. A terminating null character is always appended to the result

Warnings
Note that a null is always appended, so that if the copy is limited by the length argument, the number of characters appended to dst is n + 1.

Returns
This function returns the initial value of dst

Portability
strncat is ANSI C.

strncat requires no supporting OS subroutines.

5.30 `strncmp`—character string compare

Synopsis

#include <string.h>
int strncmp(const char *a, const char * b, size_t length);

Description
strncmp compares up to length characters from the string at a to the string at b.

Returns
If *a sorts lexicographically after *b, strncmp returns a number greater than zero. If the two strings are equivalent, strncmp returns zero. If *a sorts lexicographically before *b, strncmp returns a number less than zero.

Portability
strncmp is ANSI C.

strncmp requires no supporting OS subroutines.

5.31 `strncpy`—counted copy string

Synopsis

#include <string.h>
char *strncpy(char *restrict dst, const char *restrict src,
    size_t length);

Description
strncpy copies not more than length characters from the the string pointed to by src (including the terminating null character) to the array pointed to by dst. If the string pointed to by src is shorter than length characters, null characters are appended to the destination array until a total of length characters have been written.

Returns
This function returns the initial value of dst.

Portability
strncpy is ANSI C.

strncpy requires no supporting OS subroutines.

5.32 `strnlen`—character string length

Synopsis

#include <string.h>
size_t strnlen(const char *str, size_t n);

Description
The strnlen function works out the length of the string starting at *str by counting chararacters until it reaches a NUL character or the maximum: n number of characters have been inspected.

Returns
strnlen returns the character count or n.

Portability
strnlen is a GNU extension.

strnlen requires no supporting OS subroutines.

5.33 `strpbrk`—find characters in string

Synopsis

#include <string.h>
char *strpbrk(const char *s1, const char *s2);

Description
This function locates the first occurence in the string pointed to by s1 of any character in string pointed to by s2 (excluding the terminating null character).

Returns
strpbrk returns a pointer to the character found in s1, or a null pointer if no character from s2 occurs in s1.

Portability
strpbrk requires no supporting OS subroutines.

5.34 `strrchr`—reverse search for character in string

Synopsis

#include <string.h>
char * strrchr(const char *string, int c);

Description
This function finds the last occurence of c (converted to a char) in the string pointed to by string (including the terminating null character).

Returns
Returns a pointer to the located character, or a null pointer if c does not occur in string.

Portability
strrchr is ANSI C.

strrchr requires no supporting OS subroutines.

5.35 `strsignal`—convert signal number to string

Synopsis

#include <string.h>
char *strsignal(int signal);

Description
strsignal converts the signal number signal into a string. If signal is not a known signal number, the result will be of the form "Unknown signal NN" where NN is the signal is a decimal number.

Returns
This function returns a pointer to a string. Your application must not modify that string.

Portability
POSIX.1-2008 C requires strsignal, but does not specify the strings used for each signal number.

strsignal requires no supporting OS subroutines.

5.36 `strspn`—find initial match

Synopsis

#include <string.h>
size_t strspn(const char *s1, const char *s2);

Description
This function computes the length of the initial segment of the string pointed to by s1 which consists entirely of characters from the string pointed to by s2 (excluding the terminating null character).

Returns
strspn returns the length of the segment found.

Portability
strspn is ANSI C.

strspn requires no supporting OS subroutines.

5.37 `strstr`—find string segment

Synopsis

#include <string.h>
char *strstr(const char *s1, const char *s2);

Description
Locates the first occurrence in the string pointed to by s1 of the sequence of characters in the string pointed to by s2 (excluding the terminating null character).

Returns
Returns a pointer to the located string segment, or a null pointer if the string s2 is not found. If s2 points to a string with zero length, s1 is returned.

Portability
strstr is ANSI C.

strstr requires no supporting OS subroutines.

5.38 `strtok`, `strtok_r`, `strsep`—get next token from a string

Synopsis

#include <string.h>
char *strtok(char *restrict source,
    const char *restrict delimiters)
char *strtok_r(char *restrict source,
    const char *restrict delimiters,
    char **lasts)
char *strsep(char **source_ptr, const char *delimiters)

Description
The strtok function is used to isolate sequential tokens in a null-terminated string, *source. These tokens are delimited in the string by at least one of the characters in *delimiters. The first time that strtok is called, *source should be specified; subsequent calls, wishing to obtain further tokens from the same string, should pass a null pointer instead. The separator string, *delimiters, must be supplied each time and may change between calls.

The strtok function returns a pointer to the beginning of each subsequent token in the string, after replacing the separator character itself with a null character. When no more tokens remain, a null pointer is returned.

The strtok_r function has the same behavior as strtok, except a pointer to placeholder *lasts must be supplied by the caller.

The strsep function is similar in behavior to strtok, except a pointer to the string pointer must be supplied source_ptr and the function does not skip leading delimiters. When the string starts with a delimiter, the delimiter is changed to the null character and the empty string is returned. Like strtok_r and strtok, the *source_ptr is updated to the next character following the last delimiter found or NULL if the end of string is reached with no more delimiters.

Returns
strtok, strtok_r, and strsep all return a pointer to the next token, or NULL if no more tokens can be found. For strsep, a token may be the empty string.

Portability
strtok is ANSI C. strtok_r is POSIX. strsep is a BSD extension.

strtok, strtok_r, and strsep require no supporting OS subroutines.

5.39 `strupr`—force string to uppercase

Synopsis

#include <string.h>
char *strupr(char *a);

Description
strupr converts each character in the string at a to uppercase.

Returns
strupr returns its argument, a.

Portability
strupr is not widely portable.

strupr requires no supporting OS subroutines.

5.40 `strxfrm`—transform string

Synopsis

#include <string.h>
size_t strxfrm(char *restrict s1, const char *restrict s2,
    size_t n);

Description
This function transforms the string pointed to by s2 and places the resulting string into the array pointed to by s1. The transformation is such that if the strcmp function is applied to the two transformed strings, it returns a value greater than, equal to, or less than zero, correspoinding to the result of a strcoll function applied to the same two original strings.

No more than n characters are placed into the resulting array pointed to by s1, including the terminating null character. If n is zero, s1 may be a null pointer. If copying takes place between objects that overlap, the behavior is undefined.

With a C locale, this function just copies.

Returns
The strxfrm function returns the length of the transformed string (not including the terminating null character). If the value returned is n or more, the contents of the array pointed to by s1 are indeterminate.

Portability
strxfrm is ANSI C.

strxfrm requires no supporting OS subroutines.

5.41 `swab`—swap adjacent bytes

Synopsis

#include <unistd.h>
void swab(const void *in, void *out, ssize_t n);

Description
This function copies n bytes from the memory region pointed to by in to the memory region pointed to by out, exchanging adjacent even and odd bytes.

Portability
swab requires no supporting OS subroutines.

5.42 `wcscasecmp`—case-insensitive wide character string compare

Synopsis

#include <wchar.h>
int wcscasecmp(const wchar_t *a, const wchar_t *b);

Description
wcscasecmp compares the wide character string at a to the wide character string at b in a case-insensitive manner.

Returns

If *a sorts lexicographically after *b (after both are converted to uppercase), wcscasecmp returns a number greater than zero. If the two strings match, wcscasecmp returns zero. If *a sorts lexicographically before *b, wcscasecmp returns a number less than zero.

Portability
POSIX-1.2008

wcscasecmp requires no supporting OS subroutines. It uses tolower() from elsewhere in this library.

5.43 `wcsdup`—wide character string duplicate

Synopsis

#include <wchar.h>
wchar_t *wcsdup(const wchar_t *str);

#include <wchar.h>
wchar_t *_wcsdup_r(struct _reent *ptr, const wchar_t *str);

Description
wcsdup allocates a new wide character string using malloc, and copies the content of the argument str into the newly allocated string, thus making a copy of str.

Returns
wcsdup returns a pointer to the copy of str if enough memory for the copy was available. Otherwise it returns NULL and errno is set to ENOMEM.

Portability
POSIX-1.2008

5.44 `wcsncasecmp`—case-insensitive wide character string compare

Synopsis

#include <wchar.h>
int wcsncasecmp(const wchar_t *a, const wchar_t * b, size_t length);

Description
wcsncasecmp compares up to length wide characters from the string at a to the string at b in a case-insensitive manner.

Returns

If *a sorts lexicographically after *b (after both are converted to uppercase), wcsncasecmp returns a number greater than zero. If the two strings are equivalent, wcsncasecmp returns zero. If *a sorts lexicographically before *b, wcsncasecmp returns a number less than zero.

Portability
POSIX-1.2008

wcsncasecmp requires no supporting OS subroutines. It uses tolower() from elsewhere in this library.

6 Wide Character Strings (`wchar.h`)

This chapter describes wide-character string-handling functions and managing areas of memory containing wide characters. The corresponding declarations are in wchar.h.

• wmemchr:		Find wide character in memory
• wmemcmp:		Compare two wide-character memory areas
• wmemcpy:		Copy wide-character memory regions
• wmemmove:		Move possibly overlapping wide-character memory
• wmemset:		Set an area of memory to a specified wide character
• wcscat:		Concatenate wide-character strings
• wcschr:		Search for wide character in string
• wcscmp:		Wide-character string compare
• wcscoll:		Locale-specific wide-character string compare
• wcscpy:		Copy wide-character string
• wcpcpy:		Copy a wide-character string returning a pointer to its end
• wcscspn:		Count wide characters not in string
• wcsftime:		Convert date and time to a formatted wide-character string
• wcslcat:		Concatenate wide-character strings to specified length
• wcslcpy:		Copy wide-character string to specified length
• wcslen:		Wide-character string length
• wcsncat:		Concatenate wide-character strings
• wcsncmp:		Wide-character string compare
• wcsncpy:		Counted copy wide-character string
• wcpncpy:		Copy part of a wide-character string returning a pointer to its end
• wcsnlen:		Wide-character string length with maximum limit
• wcspbrk:		Find wide characters in string
• wcsrchr:		Reverse search for wide character in string
• wcsspn:		Find initial match in wide-character string
• wcsstr:		Find wide-character string segment
• wcstok:		Tokenize wide-character string
• wcswidth:		Number of column positions of a wide-character string
• wcsxfrm:		Locale-specific wide-character string transformation
• wcwidth:		Number of column positions of a wide-character code

6.1 `wmemchr`—find a wide character in memory

Synopsis

#include <wchar.h>
wchar_t	*wmemchr(const wchar_t *s, wchar_t c, size_t n);

Description
The wmemchr function locates the first occurrence of c in the initial n wide characters of the object pointed to be s. This function is not affected by locale and all wchar_t values are treated identically. The null wide character and wchar_t values not corresponding to valid characters are not treated specially.

If n is zero, s must be a valid pointer and the function behaves as if no valid occurrence of c is found.

Returns
The wmemchr function returns a pointer to the located wide character, or a null pointer if the wide character does not occur in the object.

Portability
wmemchr is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.2 `wmemcmp`—compare wide characters in memory

Synopsis

#include <wchar.h>
int wmemcmp(const wchar_t *s1, const wchar_t *s2, size_t n);

Description
The wmemcmp function compares the first n wide characters of the object pointed to by s1 to the first n wide characters of the object pointed to by s2. This function is not affected by locale and all wchar_t values are treated identically. The null wide character and wchar_t values not corresponding to valid characters are not treated specially.

If n is zero, s1 and s2 must be a valid pointers and the function behaves as if the two objects compare equal.

Returns
The wmemcmp function returns an integer greater than, equal to, or less than zero, accordingly as the object pointed to by s1 is greater than, equal to, or less than the object pointed to by s2.

Portability
wmemcmp is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.3 `wmemcpy`—copy wide characters in memory

Synopsis

#include <wchar.h>
wchar_t *wmemcpy(wchar_t *__restrict d,
    const wchar_t *__restrict s, size_t n);

Description
The wmemcpy function copies n wide characters from the object pointed to by s to the object pointed to be d. This function is not affected by locale and all wchar_t values are treated identically. The null wide character and wchar_t values not corresponding to valid characters are not treated specially.

If n is zero, d and s must be a valid pointers, and the function copies zero wide characters.

Returns
The wmemcpy function returns the value of d.

Portability
wmemcpy is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.4 `wmemmove`—copy wide characters in memory with overlapping areas

Synopsis

#include <wchar.h>
wchar_t *wmemmove(wchar_t *d, const wchar_t *s, size_t n);

Description
The wmemmove function copies n wide characters from the object pointed to by s to the object pointed to by d. Copying takes place as if the n wide characters from the object pointed to by s are first copied into a temporary array of n wide characters that does not overlap the objects pointed to by d or s, and then the n wide characters from the temporary array are copied into the object pointed to by d.

This function is not affected by locale and all wchar_t values are treated identically. The null wide character and wchar_t values not corresponding to valid characters are not treated specially.

If n is zero, d and s must be a valid pointers, and the function copies zero wide characters.

Returns
The wmemmove function returns the value of d.

Portability
wmemmove is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.5 `wmemset`—set wide characters in memory

Synopsis

#include <wchar.h>
wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);

Description
The wmemset function copies the value of c into each of the first n wide characters of the object pointed to by s. This function is not affected by locale and all wchar_t values are treated identically. The null wide character and wchar_t values not corresponding to valid characters are not treated specially.

If n is zero, s must be a valid pointer and the function copies zero wide characters.

Returns
The wmemset function returns the value of s.

Portability
wmemset is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.6 `wcscat`—concatenate two wide-character strings

Synopsis

#include <wchar.h>
wchar_t *wcscat(wchar_t *__restrict s1,
    const wchar_t *__restrict s2);

Description
The wcscat function appends a copy of the wide-character string pointed to by s2 (including the terminating null wide-character code) to the end of the wide-character string pointed to by s1. The initial wide-character code of s2 overwrites the null wide-character code at the end of s1. If copying takes place between objects that overlap, the behaviour is undefined.

Returns
The wcscat function returns s1; no return value is reserved to indicate an error.

Portability
wcscat is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.7 `wcschr`—wide-character string scanning operation

Synopsis

#include <wchar.h>
wchar_t *wcschr(const wchar_t *s, wchar_t c);

Description
The wcschr function locates the first occurrence of c in the wide-character string pointed to by s. The value of c must be a character representable as a type wchar_t and must be a wide-character code corresponding to a valid character in the current locale. The terminating null wide-character string.

Returns
Upon completion, wcschr returns a pointer to the wide-character code, or a null pointer if the wide-character code is not found.

Portability
wcschr is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.8 `wcscmp`—compare two wide-character strings

Synopsis

#include <wchar.h>
int wcscmp(const wchar_t *s1, *s2);

Description
The wcscmp function compares the wide-character string pointed to by s1 to the wide-character string pointed to by s2.

The sign of a non-zero return value is determined by the sign of the difference between the values of the first pair of wide-character codes that differ in the objects being compared.

Returns
Upon completion, wcscmp returns an integer greater than, equal to or less than 0, if the wide-character string pointed to by s1 is greater than, equal to or less than the wide-character string pointed to by s2 respectively.

Portability
wcscmp is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.9 `wcscoll`—locale-specific wide-character string compare

Synopsis

#include <wchar.h>
int wcscoll(const wchar_t *stra, const wchar_t * strb);

Description
wcscoll compares the wide-character string pointed to by stra to the wide-character string pointed to by strb, using an interpretation appropriate to the current LC_COLLATE state.

The current implementation of wcscoll simply uses wcscmp and does not support any language-specific sorting.

Returns
If the first string is greater than the second string, wcscoll returns a number greater than zero. If the two strings are equivalent, wcscoll returns zero. If the first string is less than the second string, wcscoll returns a number less than zero.

Portability
wcscoll is ISO/IEC 9899/AMD1:1995 (ISO C).

6.10 `wcscpy`—copy a wide-character string

Synopsis

#include <wchar.h>
wchar_t *wcscpy(wchar_t *__restrict s1,
    const wchar_t *__restrict ,s2);

Description
The wcscpy function copies the wide-character string pointed to by s2 (including the terminating null wide-character code) into the array pointed to by s1. If copying takes place between objects that overlap, the behaviour is undefined.

Returns
The wcscpy function returns s1; no return value is reserved to indicate an error.

Portability
wcscpy is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.11 `wcpcpy`—copy a wide-character string returning a pointer to its end

Synopsis

#include <wchar.h>
wchar_t *wcpcpy(wchar_t *s1, const wchar_t *,s2);

Description
The wcpcpy function copies the wide-character string pointed to by s2 (including the terminating null wide-character code) into the array pointed to by s1. If copying takes place between objects that overlap, the behaviour is undefined.

Returns
This function returns a pointer to the end of the destination string, thus pointing to the trailing ’\0’.

Portability
wcpcpy is a GNU extension.

No supporting OS subroutines are required.

6.12 `wcscspn`—get length of a complementary wide substring

Synopsis

#include <wchar.h>
size_t wcscspn(const wchar_t *s, wchar_t *set);

Description
The wcscspn function computes the length of the maximum initial segment of the wide-character string pointed to by s which consists entirely of wide-character codes not from the wide-character string pointed to by set.

Returns
The wcscspn function returns the length of the initial substring of s1; no return value is reserved to indicate an error.

Portability
wcscspn is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.13 `wcsftime`–convert date and time to a formatted wide-character string

Synopsis

#include <time.h>
#include <wchar.h>
size_t wcsftime(wchar_t *s, size_t maxsize,
    const wchar_t *format, const struct tm *timp);

Description
wcsftime is equivalent to strftime, except that:

The argument s points to the initial element of an array of wide characters into which the generated output is to be placed.
The argument maxsize indicates the limiting number of wide characters.
The argument format is a wide-character string and the conversion specifiers are replaced by corresponding sequences of wide characters.
The return value indicates the number of wide characters.

(The difference in all of the above being wide characters versus regular characters.) See strftime for the details of the format specifiers.

Returns
When the formatted time takes up no more than maxsize wide characters, the result is the length of the formatted wide string. Otherwise, if the formatting operation was abandoned due to lack of room, the result is 0, and the wide-character string starting at s corresponds to just those parts of *format that could be completely filled in within the maxsize limit.

Portability
C99 and POSIX require wcsftime, but do not specify the contents of *s when the formatted string would require more than maxsize characters. Unrecognized specifiers and fields of timp that are out of range cause undefined results. Since some formats expand to 0 bytes, it is wise to set *s to a nonzero value beforehand to distinguish between failure and an empty string. This implementation does not support s being NULL, nor overlapping s and format.

wcsftime requires no supporting OS subroutines.

See Also
strftime

6.14 `wcslcat`—concatenate wide-character strings to specified length

Synopsis

#include <wchar.h>
size_t wcslcat(wchar_t *dst, const wchar_t *src, size_t siz);

Description
The wcslcat function appends wide characters from src to end of the dst wide-character string so that the resultant wide-character string is not more than siz wide characters including the terminating null wide-character code. A terminating null wide character is always added unless siz is 0. Thus, the maximum number of wide characters that can be appended from src is siz - 1. If copying takes place between objects that overlap, the behaviour is undefined.

Returns
Wide-character string length of initial dst plus the wide-character string length of src (does not include terminating null wide-characters). If the return value is greater than or equal to siz, then truncation occurred and not all wide characters from src were appended.

Portability
No supporting OS subroutines are required.

6.15 `wcslcpy`—copy a wide-character string to specified length

Synopsis

#include <wchar.h>
size_t wcslcpy(wchar_t *dst, const wchar_t *src, size_t siz);

Description
wcslcpy copies wide characters from src to dst such that up to siz - 1 characters are copied. A terminating null is appended to the result, unless siz is zero.

Returns
wcslcpy returns the number of wide characters in src, not including the terminating null wide character. If the return value is greater than or equal to siz, then not all wide characters were copied from src and truncation occurred.

Portability
No supporting OS subroutines are required.

6.16 `wcslen`—get wide-character string length

Synopsis

#include <wchar.h>
size_t wcslen(const wchar_t *s);

Description
The wcslen function computes the number of wide-character codes in the wide-character string to which s points, not including the terminating null wide-character code.

Returns
The wcslen function returns the length of s; no return value is reserved to indicate an error.

Portability
wcslen is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.17 `wcsncat`—concatenate part of two wide-character strings

Synopsis

#include <wchar.h>
wchar_t *wcsncat(wchar_t *__restrict s1,
    const wchar_t *__restrict s2, size_t n);

Description
The wcsncat function appends not more than n wide-character codes (a null wide-character code and wide-character codes that follow it are not appended) from the array pointed to by s2 to the end of the wide-character string pointed to by s1. The initial wide-character code of s2 overwrites the null wide-character code at the end of s1. A terminating null wide-character code is always appended to the result. If copying takes place between objects that overlap, the behaviour is undefined.

Returns
The wcsncat function returns s1; no return value is reserved to indicate an error.

Portability
wcsncat is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.18 `wcsncmp`—compare part of two wide-character strings

Synopsis

#include <wchar.h>
int wcsncmp(const wchar_t *s1, const wchar_t *s2, size_t n);

Description
The wcsncmp function compares not more than n wide-character codes (wide-character codes that follow a null wide-character code are not compared) from the array pointed to by s1 to the array pointed to by s2.

The sign of a non-zero return value is determined by the sign of the difference between the values of the first pair of wide-character codes that differ in the objects being compared.

Returns
Upon successful completion, wcsncmp returns an integer greater than, equal to or less than 0, if the possibly null-terminated array pointed to by s1 is greater than, equal to or less than the possibly null-terminated array pointed to by s2 respectively.

Portability
wcsncmp is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.19 `wcsncpy`—copy part of a wide-character string

Synopsis

#include <wchar.h>
wchar_t *wcsncpy(wchar_t *__restrict s1,
    const wchar_t *__restrict s2, size_t n);

Description
The wcsncpy function copies not more than n wide-character codes (wide-character codes that follow a null wide-character code are not copied) from the array pointed to by s2 to the array pointed to by s1. If copying takes place between objects that overlap, the behaviour is undefined. Note that if s1 contains more than n wide characters before its terminating null, the result is not null-terminated.

If the array pointed to by s2 is a wide-character string that is shorter than n wide-character codes, null wide-character codes are appended to the copy in the array pointed to by s1, until n wide-character codes in all are written.

Returns
The wcsncpy function returns s1; no return value is reserved to indicate an error.

Portability
ISO/IEC 9899; POSIX.1.

No supporting OS subroutines are required.

6.20 `wcpncpy`—copy part of a wide-character string returning a pointer to its end

Synopsis

#include <wchar.h>
wchar_t *wcpncpy(wchar_t *__restrict s1,
    const wchar_t *__restrict s2, size_t n);

Description
The wcpncpy function copies not more than n wide-character codes (wide-character codes that follow a null wide-character code are not copied) from the array pointed to by s2 to the array pointed to by s1. If copying takes place between objects that overlap, the behaviour is undefined.

Returns
The wcpncpy function returns s1; no return value is reserved to indicate an error.

Portability
wcpncpy is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.21 `wcsnlen`—get fixed-size wide-character string length

Synopsis

#include <wchar.h>
size_t wcsnlen(const wchar_t *s, size_t maxlen);

Description
The wcsnlen function computes the number of wide-character codes in the wide-character string pointed to by s not including the terminating L’\0’ wide character but at most maxlen wide characters.

Returns
wcsnlen returns the length of s if it is less then maxlen, or maxlen if there is no L’\0’ wide character in first maxlen characters.

Portability
wcsnlen is a GNU extension.

wcsnlen requires no supporting OS subroutines.

6.22 `wcspbrk`—-scan wide-character string for a wide-character code

Synopsis

#include <wchar.h>
wchar_t *wcspbrk(const wchar_t *s, const wchar_t *set);

Description
The wcspbrk function locates the first occurrence in the wide-character string pointed to by s of any wide-character code from the wide-character string pointed to by set.

Returns
Upon successful completion, wcspbrk returns a pointer to the wide-character code or a null pointer if no wide-character code from set occurs in s.

Portability
wcspbrk is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.23 `wcsrchr`—wide-character string scanning operation

Synopsis

#include <wchar.h>
wchar_t *wcsrchr(const wchar_t *s, wchar_t c);

Description
The wcsrchr function locates the last occurrence of c in the wide-character string pointed to by s. The value of c must be a character representable as a type wchar_t and must be a wide-character code corresponding to a valid character in the current locale. The terminating null wide-character code is considered to be part of the wide-character string.

Returns
Upon successful completion, wcsrchr returns a pointer to the wide-character code or a null pointer if c does not occur in the wide-character string.

Portability
wcsrchr is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.24 `wcsspn`—get length of a wide substring

Synopsis

#include <wchar.h>
size_t wcsspn(const wchar_t *s, const wchar_t *set);

Description
The wcsspn function computes the length of the maximum initial segment of the wide-character string pointed to by s which consists entirely of wide-character codes from the wide-character string pointed to by set.

Returns
The wcsspn() function returns the length s1; no return value is reserved to indicate an error.

Portability
wcsspn is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.

6.25 `wcsstr`—find a wide-character substring

Synopsis

#include <wchar.h>
wchar_t *wcsstr(const wchar_t *__restrict big,
    const wchar_t *__restrict little);

Description
The wcsstr function locates the first occurrence in the wide-character string pointed to by big of the sequence of wide characters (excluding the terminating null wide character) in the wide-character string pointed to by little.

Returns
On successful completion, wcsstr returns a pointer to the located wide-character string, or a null pointer if the wide-character string is not found.

If little points to a wide-character string with zero length, the function returns big.

Portability
wcsstr is ISO/IEC 9899/AMD1:1995 (ISO C).

6.26 `wcstok`—get next token from a string

Synopsis

#include <wchar.h>
wchar_t *wcstok(wchar_t *__restrict source,
    const wchar_t *__restrict delimiters,
    wchar_t **__restrict lasts)

Description
The wcstok function is the wide-character equivalent of the strtok_r function (which in turn is the same as the strtok function with an added argument to make it thread-safe).

The wcstok function is used to isolate (one at a time) sequential tokens in a null-terminated wide-character string, *source. A token is defined as a substring not containing any wide-characters from *delimiters.

The first time that wcstok is called, *source should be specified with the wide-character string to be searched, and *lasts–but not lasts, which must be non-NULL–may be random; subsequent calls, wishing to obtain further tokens from the same string, should pass a null pointer for *source instead but must supply *lasts unchanged from the last call. The separator wide-character string, *delimiters, must be supplied each time and may change between calls. A pointer to placeholder *lasts must be supplied by the caller, and is set each time as needed to save the state by wcstok. Every call to wcstok with *source == NULL must pass the value of *lasts as last set by wcstok.

The wcstok function returns a pointer to the beginning of each subsequent token in the string, after replacing the separator wide-character itself with a null wide-character. When no more tokens remain, a null pointer is returned.

Returns
wcstok returns a pointer to the first wide character of a token, or NULL if there is no token.

Portability
wcstok is C99 and POSIX.1-2001.

wcstok requires no supporting OS subroutines.

6.27 `wcswidth`—number of column positions of a wide-character string

Synopsis

#include <wchar.h>
int wcswidth(const wchar_t *pwcs, size_t n);

Description
The wcswidth function shall determine the number of column positions required for n wide-character codes (or fewer than n wide-character codes if a null wide-character code is encountered before n wide-character codes are exhausted) in the string pointed to by pwcs.

Returns
The wcswidth function either shall return 0 (if pwcs points to a null wide-character code), or return the number of column positions to be occupied by the wide-character string pointed to by pwcs, or return -1 (if any of the first n wide-character codes in the wide-character string pointed to by pwcs is not a printable wide-character code).

Portability
wcswidth has been introduced in the Single UNIX Specification Volume 2. wcswidth has been marked as an extension in the Single UNIX Specification Volume 3.

6.28 `wcsxfrm`—locale-specific wide-character string transformation

Synopsis

#include <wchar.h>
int wcsxfrm(wchar_t *__restrict stra,
    const wchar_t *__restrict strb, size_t n);

Description
wcsxfrm transforms the wide-character string pointed to by strb to the wide-character string pointed to by stra, Comparing two transformed wide strings with wcscmp should return the same result as comparing the original strings with wcscoll. No more than n wide characters are transformed, including the trailing null character.

If n is 0, stra may be a NULL pointer.

The current implementation of wcsxfrm simply uses wcslcpy and does not support any language-specific transformations.

Returns
wcsxfrm returns the length of the transformed wide character string. if the return value is greater or equal to n, the content of stra is undefined.

Portability
wcsxfrm is ISO/IEC 9899/AMD1:1995 (ISO C).

6.29 `wcwidth`—number of column positions of a wide-character code

Synopsis

#include <wchar.h>
int wcwidth(const wchar_t wc);

Description
The wcwidth function shall determine the number of column positions required for the wide character wc. The application shall ensure that the value of wc is a character representable as a wchar_t, and is a wide-character code corresponding to a valid character in the current locale.

Returns
The wcwidth function shall either return 0 (if wc is a null wide-character code), or return the number of column positions to be occupied by the wide-character code wc, or return -1 (if wc does not correspond to a printable wide-character code).

Portability
wcwidth has been introduced in the Single UNIX Specification Volume 2. wcwidth has been marked as an extension in the Single UNIX Specification Volume 3.

7 Signal Handling (`signal.h`)

A signal is an event that interrupts the normal flow of control in your program. Your operating environment normally defines the full set of signals available (see sys/signal.h), as well as the default means of dealing with them—typically, either printing an error message and aborting your program, or ignoring the signal.

All systems support at least the following signals:

SIGABRT: Abnormal termination of a program; raised by the <<abort>> function.
SIGFPE: A domain error in arithmetic, such as overflow, or division by zero.
SIGILL: Attempt to execute as a function data that is not executable.
SIGINT: Interrupt; an interactive attention signal.
SIGSEGV: An attempt to access a memory location that is not available.
SIGTERM: A request that your program end execution.

Two functions are available for dealing with asynchronous signals—one to allow your program to send signals to itself (this is called raising a signal), and one to specify subroutines (called handlers to handle particular signals that you anticipate may occur—whether raised by your own program or the operating environment.

To support these functions, signal.h defines three macros:

SIG_DFL: Used with the signal function in place of a pointer to a handler subroutine, to select the operating environment’s default handling of a signal.
SIG_IGN: Used with the signal function in place of a pointer to a handler, to ignore a particular signal.
SIG_ERR: Returned by the signal function in place of a pointer to a handler, to indicate that your request to set up a handler could not be honored for some reason.

signal.h also defines an integral type, sig_atomic_t. This type is not used in any function declarations; it exists only to allow your signal handlers to declare a static storage location where they may store a signal value. (Static storage is not otherwise reliable from signal handlers.)

7.1 `psignal`—print a signal message on standard error

Synopsis

#include <stdio.h>
void psignal(int signal, const char *prefix);

Description
Use psignal to print (on standard error) a signal message corresponding to the value of the signal number signal. Unless you use NULL as the value of the argument prefix, the signal message will begin with the string at prefix, followed by a colon and a space (: ). The remainder of the signal message is one of the strings described for strsignal.

Returns
psignal returns no result.

Portability
POSIX.1-2008 requires psignal, but the strings issued vary from one implementation to another.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.

7.2 `raise`—send a signal

Synopsis

#include <signal.h>
int raise(int sig);

int _raise_r(void *reent, int sig);

Description
Send the signal sig (one of the macros from ‘sys/signal.h’). This interrupts your program’s normal flow of execution, and allows a signal handler (if you’ve defined one, using signal) to take control.

The alternate function _raise_r is a reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
The result is 0 if sig was successfully raised, 1 otherwise. However, the return value (since it depends on the normal flow of execution) may not be visible, unless the signal handler for sig terminates with a return or unless SIG_IGN is in effect for this signal.

Portability
ANSI C requires raise, but allows the full set of signal numbers to vary from one implementation to another.

Required OS subroutines: getpid, kill.

7.3 `signal`—specify handler subroutine for a signal

Synopsis

#include <signal.h>
void (*signal(int sig, void(*func)(int))) (int);

void (*_signal_r(void *reent, int sig, void(*func)(int))) (int);

Description
signal provides a simple signal-handling implementation for embedded targets.

signal allows you to request changed treatment for a particular signal sig. You can use one of the predefined macros SIG_DFL (select system default handling) or SIG_IGN (ignore this signal) as the value of func; otherwise, func is a function pointer that identifies a subroutine in your program as the handler for this signal.

Some of the execution environment for signal handlers is unpredictable; notably, the only library function required to work correctly from within a signal handler is signal itself, and only when used to redefine the handler for the current signal value.

Static storage is likewise unreliable for signal handlers, with one exception: if you declare a static storage location as ‘volatile sig_atomic_t’, then you may use that location in a signal handler to store signal values.

If your signal handler terminates using return (or implicit return), your program’s execution continues at the point where it was when the signal was raised (whether by your program itself, or by an external event). Signal handlers can also use functions such as exit and abort to avoid returning.

The alternate function _signal_r is the reentrant version. The extra argument reent is a pointer to a reentrancy structure.

Returns
If your request for a signal handler cannot be honored, the result is SIG_ERR; a specific error number is also recorded in errno.

Otherwise, the result is the previous handler (a function pointer or one of the predefined macros).

Portability
ANSI C requires signal.

No supporting OS subroutines are required to link with signal, but it will not have any useful effects, except for software generated signals, without an operating system that can actually raise exceptions.

8 Time Functions (`time.h`)

This chapter groups functions used either for reporting on time (elapsed, current, or compute time) or to perform calculations based on time.

The header file time.h defines three types. clock_t and time_t are both used for representations of time particularly suitable for arithmetic. (In this implementation, quantities of type clock_t have the highest resolution possible on your machine, and quantities of type time_t resolve to seconds.) size_t is also defined if necessary for quantities representing sizes.

time.h also defines the structure tm for the traditional representation of Gregorian calendar time as a series of numbers, with the following fields:

tm_sec: Seconds, between 0 and 60 inclusive (60 allows for leap seconds).
tm_min: Minutes, between 0 and 59 inclusive.
tm_hour: Hours, between 0 and 23 inclusive.
tm_mday: Day of the month, between 1 and 31 inclusive.
tm_mon: Month, between 0 (January) and 11 (December).
tm_year: Year (since 1900), can be negative for earlier years.
tm_wday: Day of week, between 0 (Sunday) and 6 (Saturday).
tm_yday: Number of days elapsed since last January 1, between 0 and 365 inclusive.
tm_isdst: Daylight Savings Time flag: positive means DST in effect, zero means DST not in effect, negative means no information about DST is available. Although for mktime(), negative means that it should decide if DST is in effect or not.

• asctime:		Format time as string
• clock:		Cumulative processor time
• ctime:		Convert time to local and format as string
• difftime:		Subtract two times
• gmtime:		Convert time to UTC (GMT) traditional representation
• localtime:		Convert time to local representation
• mktime:		Convert time to arithmetic representation
• strftime:		Convert date and time to a user-formatted string
• time:		Get current calendar time (as single number)
• __tz_lock:		Lock time zone global variables
• tzset:		Set timezone info

8.1 `asctime`—format time as string

Synopsis

#include <time.h>
char *asctime(const struct tm *clock);
char *_asctime_r(const struct tm *clock, char *buf);

Description
Format the time value at clock into a string of the form

 Wed Jun 15 11:38:07 1988\n\0

The string is generated in a static buffer; each call to asctime overwrites the string generated by previous calls.

Returns
A pointer to the string containing a formatted timestamp.

Portability
ANSI C requires asctime.

asctime requires no supporting OS subroutines.

8.2 `clock`—cumulative processor time

Synopsis

#include <time.h>
clock_t clock(void);

Description
Calculates the best available approximation of the cumulative amount of time used by your program since it started. To convert the result into seconds, divide by the macro CLOCKS_PER_SEC.

Returns
The amount of processor time used so far by your program, in units defined by the machine-dependent macro CLOCKS_PER_SEC. If no measurement is available, the result is (clock_t)-1.

Portability
ANSI C requires clock and CLOCKS_PER_SEC.

Supporting OS subroutine required: times.

8.3 `ctime`—convert time to local and format as string

Synopsis

#include <time.h>
char *ctime(const time_t *clock);
char *ctime_r(const time_t *clock, char *buf);

Description
Convert the time value at clock to local time (like localtime) and format it into a string of the form

 Wed Jun 15 11:38:07 1988\n\0

(like asctime).

Returns
A pointer to the string containing a formatted timestamp.

Portability
ANSI C requires ctime.

ctime requires no supporting OS subroutines.

8.4 `difftime`—subtract two times

Synopsis

#include <time.h>
double difftime(time_t tim1, time_t tim2);

Description
Subtracts the two times in the arguments: ‘tim1 - tim2’.

Returns
The difference (in seconds) between tim2 and tim1, as a double.

Portability
ANSI C requires difftime, and defines its result to be in seconds in all implementations.

difftime requires no supporting OS subroutines.

8.5 `gmtime`—convert time to UTC traditional form

Synopsis

#include <time.h>
struct tm *gmtime(const time_t *clock);
struct tm *gmtime_r(const time_t *clock, struct tm *res);

Description
gmtime takes the time at clock representing the number of elapsed seconds since 00:00:00 on January 1, 1970, Universal Coordinated Time (UTC, also known in some countries as GMT, Greenwich Mean time) and converts it to a struct tm representation.

gmtime constructs the traditional time representation in static storage; each call to gmtime or localtime will overwrite the information generated by previous calls to either function.

Returns
A pointer to the traditional time representation (struct tm).

Portability
ANSI C requires gmtime.

gmtime requires no supporting OS subroutines.

8.6 `localtime`—convert time to local representation

Synopsis

#include <time.h>
struct tm *localtime(time_t *clock);
struct tm *localtime_r(time_t *clock, struct tm *res);

Description
localtime converts the time at clock into local time, then converts its representation from the arithmetic representation to the traditional representation defined by struct tm.

localtime constructs the traditional time representation in static storage; each call to gmtime or localtime will overwrite the information generated by previous calls to either function.

mktime is the inverse of localtime.

Returns
A pointer to the traditional time representation (struct tm).

Portability
ANSI C requires localtime.

localtime requires no supporting OS subroutines.

8.7 `mktime`—convert time to arithmetic representation

Synopsis

#include <time.h>
time_t mktime(struct tm *timp);

Description
mktime assumes the time at timp is a local time, and converts its representation from the traditional representation defined by struct tm into a representation suitable for arithmetic.

localtime is the inverse of mktime.

Returns
If the contents of the structure at timp do not form a valid calendar time representation, the result is -1. Otherwise, the result is the time, converted to a time_t value.

Portability
ANSI C requires mktime.

mktime requires no supporting OS subroutines.

8.8 `strftime`—convert date and time to a formatted string

Synopsis

#include <time.h>
size_t strftime(char *restrict s, size_t maxsize,
    const char *restrict format,
    const struct tm *restrict timp);

Description
strftime converts a struct tm representation of the time (at timp) into a null-terminated string, starting at s and occupying no more than maxsize characters.

You control the format of the output using the string at format. *format can contain two kinds of specifications: text to be copied literally into the formatted string, and time conversion specifications. Time conversion specifications are two- and three-character sequences beginning with ‘%’ (use ‘%%’ to include a percent sign in the output). Each defined conversion specification selects only the specified field(s) of calendar time data from *timp, and converts it to a string in one of the following ways:

%a: The abbreviated weekday name according to the current locale. [tm_wday]
%A: The full weekday name according to the current locale. In the default "C" locale, one of ‘Sunday’, ‘Monday’, ‘Tuesday’, ‘Wednesday’, ‘Thursday’, ‘Friday’, ‘Saturday’. [tm_wday]
%b: The abbreviated month name according to the current locale. [tm_mon]
%B: The full month name according to the current locale. In the default "C" locale, one of ‘January’, ‘February’, ‘March’, ‘April’, ‘May’, ‘June’, ‘July’, ‘August’, ‘September’, ‘October’, ‘November’, ‘December’. [tm_mon]
%c: The preferred date and time representation for the current locale. [tm_sec, tm_min, tm_hour, tm_mday, tm_mon, tm_year, tm_wday]
%C: The century, that is, the year divided by 100 then truncated. For 4-digit years, the result is zero-padded and exactly two characters; but for other years, there may a negative sign or more digits. In this way, ‘%C%y’ is equivalent to ‘%Y’. [tm_year]
%d: The day of the month, formatted with two digits (from ‘01’ to ‘31’). [tm_mday]
%D: A string representing the date, in the form ‘"%m/%d/%y"’. [tm_mday, tm_mon, tm_year]
%e: The day of the month, formatted with leading space if single digit (from ‘1’ to ‘31’). [tm_mday]
%Ex: In some locales, the E modifier selects alternative representations of certain modifiers x. In newlib, it is ignored, and treated as %x.
%F: A string representing the ISO 8601:2000 date format, in the form ‘"%Y-%m-%d"’. [tm_mday, tm_mon, tm_year]
%g: The last two digits of the week-based year, see specifier %G (from ‘00’ to ‘99’). [tm_year, tm_wday, tm_yday]
%G: The week-based year. In the ISO 8601:2000 calendar, week 1 of the year includes January 4th, and begin on Mondays. Therefore, if January 1st, 2nd, or 3rd falls on a Sunday, that day and earlier belong to the last week of the previous year; and if December 29th, 30th, or 31st falls on Monday, that day and later belong to week 1 of the next year. For consistency with %Y, it always has at least four characters. Example: "%G" for Saturday 2nd January 1999 gives "1998", and for Tuesday 30th December 1997 gives "1998". [tm_year, tm_wday, tm_yday]
%h: Synonym for "%b". [tm_mon]
%H: The hour (on a 24-hour clock), formatted with two digits (from ‘00’ to ‘23’). [tm_hour]
%I: The hour (on a 12-hour clock), formatted with two digits (from ‘01’ to ‘12’). [tm_hour]
%j: The count of days in the year, formatted with three digits (from ‘001’ to ‘366’). [tm_yday]
%k: The hour (on a 24-hour clock), formatted with leading space if single digit (from ‘0’ to ‘23’). Non-POSIX extension (c.p. %I). [tm_hour]
%l: The hour (on a 12-hour clock), formatted with leading space if single digit (from ‘1’ to ‘12’). Non-POSIX extension (c.p. %H). [tm_hour]
%m: The month number, formatted with two digits (from ‘01’ to ‘12’). [tm_mon]
%M: The minute, formatted with two digits (from ‘00’ to ‘59’). [tm_min]
%n: A newline character (‘\n’).
%Ox: In some locales, the O modifier selects alternative digit characters for certain modifiers x. In newlib, it is ignored, and treated as %x.
%p: Either ‘AM’ or ‘PM’ as appropriate, or the corresponding strings for the current locale. [tm_hour]
%P: Same as ’%p’, but in lowercase. This is a GNU extension. [tm_hour]
%r: Replaced by the time in a.m. and p.m. notation. In the "C" locale this is equivalent to "%I:%M:%S %p". In locales which don’t define a.m./p.m. notations, the result is an empty string. [tm_sec, tm_min, tm_hour]
%R: The 24-hour time, to the minute. Equivalent to "%H:%M". [tm_min, tm_hour]
%S: The second, formatted with two digits (from ‘00’ to ‘60’). The value 60 accounts for the occasional leap second. [tm_sec]
%t: A tab character (‘\t’).
%T: The 24-hour time, to the second. Equivalent to "%H:%M:%S". [tm_sec, tm_min, tm_hour]
%u: The weekday as a number, 1-based from Monday (from ‘1’ to ‘7’). [tm_wday]
%U: The week number, where weeks start on Sunday, week 1 contains the first Sunday in a year, and earlier days are in week 0. Formatted with two digits (from ‘00’ to ‘53’). See also %W. [tm_wday, tm_yday]
%V: The week number, where weeks start on Monday, week 1 contains January 4th, and earlier days are in the previous year. Formatted with two digits (from ‘01’ to ‘53’). See also %G. [tm_year, tm_wday, tm_yday]
%w: The weekday as a number, 0-based from Sunday (from ‘0’ to ‘6’). [tm_wday]
%W: The week number, where weeks start on Monday, week 1 contains the first Monday in a year, and earlier days are in week 0. Formatted with two digits (from ‘00’ to ‘53’). [tm_wday, tm_yday]
%x: Replaced by the preferred date representation in the current locale. In the "C" locale this is equivalent to "%m/%d/%y". [tm_mon, tm_mday, tm_year]
%X: Replaced by the preferred time representation in the current locale. In the "C" locale this is equivalent to "%H:%M:%S". [tm_sec, tm_min, tm_hour]
%y: The last two digits of the year (from ‘00’ to ‘99’). [tm_year] (Implementation interpretation: always positive, even for negative years.)
%Y: The full year, equivalent to %C%y. It will always have at least four characters, but may have more. The year is accurate even when tm_year added to the offset of 1900 overflows an int. [tm_year]
%z: The offset from UTC. The format consists of a sign (negative is west of Greewich), two characters for hour, then two characters for minutes (-hhmm or +hhmm). If tm_isdst is negative, the offset is unknown and no output is generated; if it is zero, the offset is the standard offset for the current time zone; and if it is positive, the offset is the daylight savings offset for the current timezone. The offset is determined from the TZ environment variable, as if by calling tzset(). [tm_isdst]
%Z: The time zone name. If tm_isdst is negative, no output is generated. Otherwise, the time zone name is based on the TZ environment variable, as if by calling tzset(). [tm_isdst]
%%: A single character, ‘%’.

Returns
When the formatted time takes up no more than maxsize characters, the result is the length of the formatted string. Otherwise, if the formatting operation was abandoned due to lack of room, the result is 0, and the string starting at s corresponds to just those parts of *format that could be completely filled in within the maxsize limit.

Portability
ANSI C requires strftime, but does not specify the contents of *s when the formatted string would require more than maxsize characters. Unrecognized specifiers and fields of timp that are out of range cause undefined results. Since some formats expand to 0 bytes, it is wise to set *s to a nonzero value beforehand to distinguish between failure and an empty string. This implementation does not support s being NULL, nor overlapping s and format.

strftime requires no supporting OS subroutines.

Bugs
strftime ignores the LC_TIME category of the current locale, hard-coding the "C" locale settings.

8.9 `time`—get current calendar time (as single number)

Synopsis

#include <time.h>
time_t time(time_t *t);

Description
time looks up the best available representation of the current time and returns it, encoded as a time_t. It stores the same value at t unless the argument is NULL.

Returns
A -1 result means the current time is not available; otherwise the result represents the current time.

Portability
ANSI C requires time.

Supporting OS subroutine required: Some implementations require gettimeofday.

8.10 `__tz_lock`, `__tz_unlock`—lock time zone global variables

Synopsis

#include "local.h"
void __tz_lock (void);
void __tz_unlock (void);

Description
The tzset facility functions call these functions when they need to ensure the values of global variables. The version of these routines supplied in the library use the lock API defined in sys/lock.h. If multiple threads of execution can call the time functions and give up scheduling in the middle, then you you need to define your own versions of these functions in order to safely lock the time zone variables during a call. If you do not, the results of localtime, mktime, ctime, and strftime are undefined.

The lock __tz_lock may not be called recursively; that is, a call __tz_lock will always lock all subsequent __tz_lock calls until the corresponding __tz_unlock call on the same thread is made.

8.11 `tzset`—set timezone characteristics from TZ environment variable

Synopsis

#include <time.h>
void tzset(void);
void _tzset_r (struct _reent *);

Description
tzset examines the TZ environment variable and sets up the three external variables: _timezone, _daylight, and tzname. The value of _timezone shall be the offset from the current time zone to GMT. The value of _daylight shall be 0 if there is no daylight savings time for the current time zone, otherwise it will be non-zero. The tzname array has two entries: the first is the name of the standard time zone, the second is the name of the daylight-savings time zone.

The TZ environment variable is expected to be in the following POSIX format:

stdoffset1[dst[offset2][,start[/time1],end[/time2]]]

where: std is the name of the standard time-zone (minimum 3 chars) offset1 is the value to add to local time to arrive at Universal time it has the form: hh[:mm[:ss]] dst is the name of the alternate (daylight-savings) time-zone (min 3 chars) offset2 is the value to add to local time to arrive at Universal time it has the same format as the std offset start is the day that the alternate time-zone starts time1 is the optional time that the alternate time-zone starts (this is in local time and defaults to 02:00:00 if not specified) end is the day that the alternate time-zone ends time2 is the time that the alternate time-zone ends (it is in local time and defaults to 02:00:00 if not specified)

Note that there is no white-space padding between fields. Also note that if TZ is null, the default is Universal GMT which has no daylight-savings time. If TZ is empty, the default EST5EDT is used.

The function _tzset_r is identical to tzset only it is reentrant and is used for applications that use multiple threads.

Returns
There is no return value.

Portability
tzset is part of the POSIX standard.

Supporting OS subroutine required: None

9 Locale (`locale.h`)

A locale is the name for a collection of parameters (affecting collating sequences and formatting conventions) that may be different depending on location or culture. The "C" locale is the only one defined in the ANSI C standard.

This is a minimal implementation, supporting only the required "C" value for locale; strings representing other locales are not honored. ("" is also accepted; it represents the default locale for an implementation, here equivalent to "C".

locale.h defines the structure lconv to collect the information on a locale, with the following fields:

char *decimal_point: The decimal point character used to format “ordinary” numbers (all numbers except those referring to amounts of money). "." in the C locale.
char *thousands_sep: The character (if any) used to separate groups of digits, when formatting ordinary numbers. "" in the C locale.
char *grouping: Specifications for how many digits to group (if any grouping is done at all) when formatting ordinary numbers. The numeric value of each character in the string represents the number of digits for the next group, and a value of 0 (that is, the string’s trailing NULL) means to continue grouping digits using the last value specified. Use CHAR_MAX to indicate that no further grouping is desired. "" in the C locale.
char *int_curr_symbol: The international currency symbol (first three characters), if any, and the character used to separate it from numbers. "" in the C locale.
char *currency_symbol: The local currency symbol, if any. "" in the C locale.
char *mon_decimal_point: The symbol used to delimit fractions in amounts of money. "" in the C locale.
char *mon_thousands_sep: Similar to thousands_sep, but used for amounts of money. "" in the C locale.
char *mon_grouping: Similar to grouping, but used for amounts of money. "" in the C locale.
char *positive_sign: A string to flag positive amounts of money when formatting. "" in the C locale.
char *negative_sign: A string to flag negative amounts of money when formatting. "" in the C locale.
char int_frac_digits: The number of digits to display when formatting amounts of money to international conventions. CHAR_MAX (the largest number representable as a char) in the C locale.
char frac_digits: The number of digits to display when formatting amounts of money to local conventions. CHAR_MAX in the C locale.
char p_cs_precedes: 1 indicates the local currency symbol is used before a positive or zero formatted amount of money; 0 indicates the currency symbol is placed after the formatted number. CHAR_MAX in the C locale.
char p_sep_by_space: 1 indicates the local currency symbol must be separated from positive or zero numbers by a space; 0 indicates that it is immediately adjacent to numbers. CHAR_MAX in the C locale.
char n_cs_precedes: 1 indicates the local currency symbol is used before a negative formatted amount of money; 0 indicates the currency symbol is placed after the formatted number. CHAR_MAX in the C locale.
char n_sep_by_space: 1 indicates the local currency symbol must be separated from negative numbers by a space; 0 indicates that it is immediately adjacent to numbers. CHAR_MAX in the C locale.
char p_sign_posn: Controls the position of the positive sign for numbers representing money. 0 means parentheses surround the number; 1 means the sign is placed before both the number and the currency symbol; 2 means the sign is placed after both the number and the currency symbol; 3 means the sign is placed just before the currency symbol; and 4 means the sign is placed just after the currency symbol. CHAR_MAX in the C locale.
char n_sign_posn: Controls the position of the negative sign for numbers representing money, using the same rules as p_sign_posn. CHAR_MAX in the C locale.

9.1 `setlocale`, `localeconv`—select or query locale

Synopsis

#include <locale.h>
char *setlocale(int category, const char *locale);
lconv *localeconv(void);

char *_setlocale_r(void *reent,
    int category, const char *locale);
lconv *_localeconv_r(void *reent);

Description
setlocale is the facility defined by ANSI C to condition the execution environment for international collating and formatting information; localeconv reports on the settings of the current locale.

This is a minimal implementation, supporting only the required "POSIX" and "C" values for locale; strings representing other locales are not honored unless _MB_CAPABLE is defined.

If _MB_CAPABLE is defined, POSIX locale strings are allowed, following the form

language[_TERRITORY][.charset][@modifier]

"language" is a two character string per ISO 639, or, if not available for a given language, a three character string per ISO 639-3. "TERRITORY" is a country code per ISO 3166. For "charset" and "modifier" see below.

Additionally to the POSIX specifier, the following extension is supported for backward compatibility with older implementations using newlib: "C-charset". Instead of "C-", you can also specify "C.". Both variations allow to specify language neutral locales while using other charsets than ASCII, for instance "C.UTF-8", which keeps all settings as in the C locale, but uses the UTF-8 charset.

The following charsets are recognized: "UTF-8", "JIS", "EUCJP", "SJIS", "KOI8-R", "KOI8-U", "GEORGIAN-PS", "PT154", "TIS-620", "ISO-8859-x" with 1 <= x <= 16, or "CPxxx" with xxx in [437, 720, 737, 775, 850, 852, 855, 857, 858, 862, 866, 874, 932, 1125, 1250, 1251, 1252, 1253, 1254, 1255, 1256, 1257, 1258].

Charsets are case insensitive. For instance, "EUCJP" and "eucJP" are equivalent. Charset names with dashes can also be written without dashes, as in "UTF8", "iso88591" or "koi8r". "EUCJP" and "EUCKR" are also recognized with dash, "EUC-JP" and "EUC-KR".

Full support for all of the above charsets requires that newlib has been build with multibyte support and support for all ISO and Windows Codepage. Otherwise all singlebyte charsets are simply mapped to ASCII. Right now, only newlib for Cygwin is built with full charset support by default. Under Cygwin, this implementation additionally supports the charsets "GBK", "GB2312", "eucCN", "eucKR", and "Big5". Cygwin does not support "JIS".

Cygwin additionally supports locales from the file /usr/share/locale/locale.alias.

("" is also accepted; if given, the settings are read from the corresponding LC_* environment variables and $LANG according to POSIX rules.

This implementation also supports the modifier "cjknarrow", which affects how the functions wcwidth and wcswidth handle characters from the "CJK Ambiguous Width" category of characters described at http://www.unicode.org/reports/tr11/#Ambiguous. These characters have a width of 1 for singlebyte charsets and a width of 2 for multibyte charsets other than UTF-8. For UTF-8, their width depends on the language specifier: it is 2 for "zh" (Chinese), "ja" (Japanese), and "ko" (Korean), and 1 for everything else. Specifying "cjknarrow" forces a width of 1, independent of charset and language.

If you use NULL as the locale argument, setlocale returns a pointer to the string representing the current locale. The acceptable values for category are defined in ‘locale.h’ as macros beginning with "LC_".

localeconv returns a pointer to a structure (also defined in ‘locale.h’) describing the locale-specific conventions currently in effect.

_localeconv_r and _setlocale_r are reentrant versions of localeconv and setlocale respectively. The extra argument reent is a pointer to a reentrancy structure.

Returns
A successful call to setlocale returns a pointer to a string associated with the specified category for the new locale. The string returned by setlocale is such that a subsequent call using that string will restore that category (or all categories in case of LC_ALL), to that state. The application shall not modify the string returned which may be overwritten by a subsequent call to setlocale. On error, setlocale returns NULL.

localeconv returns a pointer to a structure of type lconv, which describes the formatting and collating conventions in effect (in this implementation, always those of the C locale).

Portability
ANSI C requires setlocale, but the only locale required across all implementations is the C locale.

10 Reentrancy

Reentrancy is a characteristic of library functions which allows multiple processes to use the same address space with assurance that the values stored in those spaces will remain constant between calls. The Red Hat newlib implementation of the library functions ensures that whenever possible, these library functions are reentrant. However, there are some functions that can not be trivially made reentrant. Hooks have been provided to allow you to use these functions in a fully reentrant fashion.

These hooks use the structure _reent defined in reent.h. A variable defined as ‘struct _reent’ is called a reentrancy structure. All functions which must manipulate global information are available in two versions. The first version has the usual name, and uses a single global instance of the reentrancy structure. The second has a different name, normally formed by prepending ‘_’ and appending ‘_r’, and takes a pointer to the particular reentrancy structure to use.

For example, the function fopen takes two arguments, file and mode, and uses the global reentrancy structure. The function _fopen_r takes the arguments, struct_reent, which is a pointer to an instance of the reentrancy structure, file and mode.

There are two versions of ‘struct _reent’, a normal one and one for small memory systems, controlled by the _REENT_SMALL definition from the (automatically included) <sys/config.h>.

Each function which uses the global reentrancy structure uses the global variable _impure_ptr, which points to a reentrancy structure.

This means that you have two ways to achieve reentrancy. Both require that each thread of execution control initialize a unique global variable of type ‘struct _reent’:

Use the reentrant versions of the library functions, after initializing a global reentrancy structure for each process. Use the pointer to this structure as the extra argument for all library functions.
Ensure that each thread of execution control has a pointer to its own unique reentrancy structure in the global variable _impure_ptr, and call the standard library subroutines.

The following functions are provided in both reentrant and non-reentrant versions.

Equivalent for errno variable:

_errno_r

Locale functions:

_localeconv_r  _setlocale_r

Equivalents for stdio variables:

_stdin_r        _stdout_r       _stderr_r

Stdio functions:

_fdopen_r       _perror_r       _tempnam_r
_fopen_r        _putchar_r      _tmpnam_r
_getchar_r      _puts_r         _tmpfile_r
_gets_r         _remove_r       _vfprintf_r
_iprintf_r      _rename_r       _vsnprintf_r
_mkstemp_r      _snprintf_r     _vsprintf_r
_mktemp_t       _sprintf_r

Signal functions:

_init_signal_r  _signal_r
_kill_r         __sigtramp_r
_raise_r

Stdlib functions:

_calloc_r       _mblen_r        _setenv_r
_dtoa_r         _mbstowcs_r     _srand_r
_free_r         _mbtowc_r       _strtod_r
_getenv_r       _memalign_r     _strtol_r
_mallinfo_r     _mstats_r       _strtoul_r
_malloc_r       _putenv_r       _system_r
_malloc_r       _rand_r         _wcstombs_r
_malloc_stats_r _realloc_r      _wctomb_r

String functions:

_strdup_r       _strtok_r

System functions:

_close_r        _link_r         _unlink_r
_execve_r       _lseek_r        _wait_r
_fcntl_r        _open_r         _write_r 
_fork_r         _read_r
_fstat_r        _sbrk_r
_gettimeofday_r _stat_r
_getpid_r       _times_r

Time function:

_asctime_r

11 Miscellaneous Macros and Functions

This chapter describes miscellaneous routines not covered elsewhere.

11.1 `ffs`—find first bit set in a word

Synopsis

#include <strings.h>
int ffs(int word);

Description

ffs returns the first bit set in a word.

Returns
ffs returns 0 if c is 0, 1 if c is odd, 2 if c is a multiple of 2, etc.

Portability
ffs is not ANSI C.

No supporting OS subroutines are required.

11.2 `unctrl`—get printable representation of a character

Synopsis

#include <unctrl.h>
char *unctrl(int c);
int unctrllen(int c);

Description
unctrl is a macro which returns the printable representation of c as a string. unctrllen is a macro which returns the length of the printable representation of c.

Returns
unctrl returns a string of the printable representation of c.

unctrllen returns the length of the string which is the printable representation of c.

Portability
unctrl and unctrllen are not ANSI C.

No supporting OS subroutines are required.

12 System Calls

The C subroutine library depends on a handful of subroutine calls for operating system services. If you use the C library on a system that complies with the POSIX.1 standard (also known as IEEE 1003.1), most of these subroutines are supplied with your operating system.

If some of these subroutines are not provided with your system—in the extreme case, if you are developing software for a “bare board” system, without an OS—you will at least need to provide do-nothing stubs (or subroutines with minimal functionality) to allow your programs to link with the subroutines in libc.a.

12.1 Definitions for OS interface

This is the complete set of system definitions (primarily subroutines) required; the examples shown implement the minimal functionality required to allow libc to link, and fail gracefully where OS services are not available.

Graceful failure is permitted by returning an error code. A minor complication arises here: the C library must be compatible with development environments that supply fully functional versions of these subroutines. Such environments usually return error codes in a global errno. However, the Red Hat newlib C library provides a macro definition for errno in the header file errno.h, as part of its support for reentrant routines (see Reentrancy).

The bridge between these two interpretations of errno is straightforward: the C library routines with OS interface calls capture the errno values returned globally, and record them in the appropriate field of the reentrancy structure (so that you can query them using the errno macro from errno.h).

This mechanism becomes visible when you write stub routines for OS interfaces. You must include errno.h, then disable the macro, like this:

#include <errno.h>
#undef errno
extern int errno;

The examples in this chapter include this treatment of errno.

_exit

Exit a program without cleaning up files. If your system doesn’t provide this, it is best to avoid linking with subroutines that require it (exit, system).

close

Close a file. Minimal implementation:

int close(int file) {
  return -1;
}

environ

A pointer to a list of environment variables and their values. For a minimal environment, this empty list is adequate:

char *__env[1] = { 0 };
char **environ = __env;

execve

Transfer control to a new process. Minimal implementation (for a system without processes):

#include <errno.h>
#undef errno
extern int errno;
int execve(char *name, char **argv, char **env) {
  errno = ENOMEM;
  return -1;
}

fork

Create a new process. Minimal implementation (for a system without processes):

#include <errno.h>
#undef errno
extern int errno;
int fork(void) {
  errno = EAGAIN;
  return -1;
}

fstat

Status of an open file. For consistency with other minimal implementations in these examples, all files are regarded as character special devices. The sys/stat.h header file required is distributed in the include subdirectory for this C library.

#include <sys/stat.h>
int fstat(int file, struct stat *st) {
  st->st_mode = S_IFCHR;
  return 0;
}

getpid

Process-ID; this is sometimes used to generate strings unlikely to conflict with other processes. Minimal implementation, for a system without processes:

int getpid(void) {
  return 1;
}

isatty

Query whether output stream is a terminal. For consistency with the other minimal implementations, which only support output to stdout, this minimal implementation is suggested:

int isatty(int file) {
  return 1;
}

kill

Send a signal. Minimal implementation:

#include <errno.h>
#undef errno
extern int errno;
int kill(int pid, int sig) {
  errno = EINVAL;
  return -1;
}

link

Establish a new name for an existing file. Minimal implementation:

#include <errno.h>
#undef errno
extern int errno;
int link(char *old, char *new) {
  errno = EMLINK;
  return -1;
}

lseek

Set position in a file. Minimal implementation:

int lseek(int file, int ptr, int dir) {
  return 0;
}

open

Open a file. Minimal implementation:

int open(const char *name, int flags, int mode) {
  return -1;
}

read

Read from a file. Minimal implementation:

int read(int file, char *ptr, int len) {
  return 0;
}

sbrk

Increase program data space. As malloc and related functions depend on this, it is useful to have a working implementation. The following suffices for a standalone system; it exploits the symbol _end automatically defined by the GNU linker.

caddr_t sbrk(int incr) {
  extern char _end;		/* Defined by the linker */
  static char *heap_end;
  char *prev_heap_end;
 
  if (heap_end == 0) {
    heap_end = &_end;
  }
  prev_heap_end = heap_end;
  if (heap_end + incr > stack_ptr) {
    write (1, "Heap and stack collision\n", 25);
    abort ();
  }

  heap_end += incr;
  return (caddr_t) prev_heap_end;
}

stat

Status of a file (by name). Minimal implementation:

int stat(char *file, struct stat *st) {
  st->st_mode = S_IFCHR;
  return 0;
}

times

Timing information for current process. Minimal implementation:

int times(struct tms *buf) {
  return -1;
}

unlink

Remove a file’s directory entry. Minimal implementation:

#include <errno.h>
#undef errno
extern int errno;
int unlink(char *name) {
  errno = ENOENT;
  return -1; 
}

wait

Wait for a child process. Minimal implementation:

#include <errno.h>
#undef errno
extern int errno;
int wait(int *status) {
  errno = ECHILD;
  return -1;
}

write

Write to a file. libc subroutines will use this system routine for output to all files, including stdout—so if you need to generate any output, for example to a serial port for debugging, you should make your minimal write capable of doing this. The following minimal implementation is an incomplete example; it relies on a outbyte subroutine (not shown; typically, you must write this in assembler from examples provided by your hardware manufacturer) to actually perform the output.

int write(int file, char *ptr, int len) {
  int todo;

  for (todo = 0; todo < len; todo++) {
    outbyte (*ptr++);
  }
  return len;
}

12.2 Reentrant covers for OS subroutines

Since the system subroutines are used by other library routines that require reentrancy, libc.a provides cover routines (for example, the reentrant version of fork is _fork_r). These cover routines are consistent with the other reentrant subroutines in this library, and achieve reentrancy by using a reserved global data block (see Reentrancy).

_open_r

A reentrant version of open. It takes a pointer to the global data block, which holds errno.

int _open_r(void *reent,
    const char *file, int flags, int mode);

_close_r

A reentrant version of close. It takes a pointer to the global data block, which holds errno.

int _close_r(void *reent, int fd);

_lseek_r

A reentrant version of lseek. It takes a pointer to the global data block, which holds errno.

off_t _lseek_r(void *reent,
    int fd, off_t pos, int whence);

_read_r

A reentrant version of read. It takes a pointer to the global data block, which holds errno.

long _read_r(void *reent,
    int fd, void *buf, size_t cnt);

_write_r

A reentrant version of write. It takes a pointer to the global data block, which holds errno.

long _write_r(void *reent,
    int fd, const void *buf, size_t cnt);

_fork_r

A reentrant version of fork. It takes a pointer to the global data block, which holds errno.

int _fork_r(void *reent);

_wait_r

A reentrant version of wait. It takes a pointer to the global data block, which holds errno.

int _wait_r(void *reent, int *status);

_stat_r

A reentrant version of stat. It takes a pointer to the global data block, which holds errno.

int _stat_r(void *reent,
    const char *file, struct stat *pstat);

_fstat_r

A reentrant version of fstat. It takes a pointer to the global data block, which holds errno.

int _fstat_r(void *reent,
    int fd, struct stat *pstat);

_link_r

A reentrant version of link. It takes a pointer to the global data block, which holds errno.

int _link_r(void *reent,
    const char *old, const char *new);

_unlink_r

A reentrant version of unlink. It takes a pointer to the global data block, which holds errno.

int _unlink_r(void *reent, const char *file);

_sbrk_r

A reentrant version of sbrk. It takes a pointer to the global data block, which holds errno.

char *_sbrk_r(void *reent, size_t incr);

13 Variable Argument Lists

The printf family of functions is defined to accept a variable number of arguments, rather than a fixed argument list. You can define your own functions with a variable argument list, by using macro definitions from either stdarg.h (for compatibility with ANSI C) or from varargs.h (for compatibility with a popular convention prior to ANSI C).

13.1 ANSI-standard macros, `stdarg.h`

In ANSI C, a function has a variable number of arguments when its parameter list ends in an ellipsis (...). The parameter list must also include at least one explicitly named argument; that argument is used to initialize the variable list data structure.

ANSI C defines three macros (va_start, va_arg, and va_end) to operate on variable argument lists. stdarg.h also defines a special type to represent variable argument lists: this type is called va_list.

13.1.1 Initialize variable argument list

Synopsis

#include <stdarg.h>
void va_start(va_list ap, rightmost);

Description
Use va_start to initialize the variable argument list ap, so that va_arg can extract values from it. rightmost is the name of the last explicit argument in the parameter list (the argument immediately preceding the ellipsis ‘...’ that flags variable arguments in an ANSI C function header). You can only use va_start in a function declared using this ellipsis notation (not, for example, in one of its subfunctions).

Returns
va_start does not return a result.

Portability
ANSI C requires va_start.

13.1.2 Extract a value from argument list

Synopsis

#include <stdarg.h>
type va_arg(va_list ap, type);

Description
va_arg returns the next unprocessed value from a variable argument list ap (which you must previously create with va_start). Specify the type for the value as the second parameter to the macro, type.

You may pass a va_list object ap to a subfunction, and use va_arg from the subfunction rather than from the function actually declared with an ellipsis in the header; however, in that case you may only use va_arg from the subfunction. ANSI C does not permit extracting successive values from a single variable-argument list from different levels of the calling stack.

There is no mechanism for testing whether there is actually a next argument available; you might instead pass an argument count (or some other data that implies an argument count) as one of the fixed arguments in your function call.

Returns
va_arg returns the next argument, an object of type type.

Portability
ANSI C requires va_arg.

13.1.3 Abandon a variable argument list

Synopsis

#include <stdarg.h>
void va_end(va_list ap);

Description
Use va_end to declare that your program will not use the variable argument list ap any further.

Returns
va_end does not return a result.

Portability
ANSI C requires va_end.

13.2 Traditional macros, `varargs.h`

If your C compiler predates ANSI C, you may still be able to use variable argument lists using the macros from the varargs.h header file. These macros resemble their ANSI counterparts, but have important differences in usage. In particular, since traditional C has no declaration mechanism for variable argument lists, two additional macros are provided simply for the purpose of defining functions with variable argument lists.

As with stdarg.h, the type va_list is used to hold a data structure representing a variable argument list.

13.2.1 Declare variable arguments

Synopsis

#include <varargs.h>
function(va_alist)
va_dcl

Description
To use the varargs.h version of variable argument lists, you must declare your function with a call to the macro va_alist as its argument list, and use va_dcl as the declaration. Do not use a semicolon after va_dcl.

Returns
These macros cannot be used in a context where a return is syntactically possible.

Portability
va_alist and va_dcl were the most widespread method of declaring variable argument lists prior to ANSI C.

13.2.2 Initialize variable argument list

Synopsis

#include <varargs.h>
va_list ap;
va_start(ap);

Description
With the varargs.h macros, use va_start to initialize a data structure ap to permit manipulating a variable argument list. ap must have the type va_alist.

Returns
va_start does not return a result.

Portability
va_start is also defined as a macro in ANSI C, but the definitions are incompatible; the ANSI version has another parameter besides ap.

13.2.3 Extract a value from argument list

Synopsis

#include <varargs.h>
type va_arg(va_list ap, type);

Returns
va_arg returns the next argument, an object of type type.

Portability
The va_arg defined in varargs.h has the same syntax and usage as the ANSI C version from stdarg.h.

13.2.4 Abandon a variable argument list

Synopsis

#include <varargs.h>
va_end(va_list ap);

Description
Use va_end to declare that your program will not use the variable argument list ap any further.

Returns
va_end does not return a result.

Portability
The va_end defined in varargs.h has the same syntax and usage as the ANSI C version from stdarg.h.

Document Index

Jump to:	_ A B C D E F G I J K L M N O P Q R S T U V W

	Index Entry	Section

_
	`_asctime_r`:	asctime
	`_asiprintf_r`:	siprintf
	`_asniprintf_r`:	siprintf
	`_asnprintf_r`:	sprintf
	`_asprintf_r`:	sprintf
	`_atoi_r`:	atoi
	`_atoll_r`:	atoll
	`_atol_r`:	atoi
	`_calloc_r`:	calloc
	`_close_r`:	Reentrant Syscalls
	`_diprintf_r`:	diprintf
	`_dprintf_r`:	dprintf
	`_Exit`:	_Exit
	`_exit`:	Stubs
	`_fcloseall_r`:	fcloseall
	`_fclose_r`:	fclose
	`_fdopen_r`:	fdopen
	`_fflush_r`:	fflush
	`_fflush_unlocked_r`:	fflush
	`_fgetc_r`:	fgetc
	`_fgetc_unlocked_r`:	fgetc
	`_fgetpos_r`:	fgetpos
	`_fgets_r`:	fgets
	`_fgets_unlocked_r`:	fgets
	`_fgetwc_r`:	fgetwc
	`_fgetwc_unlocked_r`:	fgetwc
	`_fgetws_r`:	fgetws
	`_fgetws_unlocked_r`:	fgetws
	`_fiprintf_r`:	siprintf
	`_fiscanf_r`:	siscanf
	`_fopen_r`:	fopen
	`_fork_r`:	Reentrant Syscalls
	`_fprintf_r`:	sprintf
	`_fpurge_r`:	fpurge
	`_fputc_r`:	fputc
	`_fputc_unlocked_r`:	fputc
	`_fputs_r`:	fputs
	`_fputs_unlocked_r`:	fputs
	`_fputwc_r`:	fputwc
	`_fputwc_unlocked_r`:	fputwc
	`_fputws_r`:	fputws
	`_fputws_unlocked_r`:	fputws
	`_fread_r`:	fread
	`_fread_unlocked_r`:	fread
	`_free_r`:	malloc
	`_freopen_r`:	freopen
	`_fscanf_r`:	sscanf
	`_fseeko_r`:	fseek
	`_fseek_r`:	fseek
	`_fsetpos_r`:	fsetpos
	`_fstat_r`:	Reentrant Syscalls
	`_ftello_r`:	ftell
	`_ftell_r`:	ftell
	`_fwide_r`:	fwide
	`_fwprintf_r`:	swprintf
	`_fwrite_r`:	fwrite
	`_fwrite_unlocked_r`:	fwrite
	`_fwscanf_r`:	swscanf
	`_getchar_r`:	getchar
	`_getchar_unlocked_r`:	getchar_unlocked
	`_getc_r`:	getc
	`_getc_unlocked_r`:	getc_unlocked
	`_gets_r`:	gets
	`_getwchar_r`:	getwchar
	`_getwchar_unlocked_r`:	getwchar
	`_getwc_r`:	fgetwc
	`_getwc_unlocked_r`:	fgetwc
	`_impure_ptr`:	Reentrancy
	`_iprintf_r`:	siprintf
	`_iscanf_r`:	siscanf
	`_link_r`:	Reentrant Syscalls
	`_localeconv_r`:	setlocale
	`_lseek_r`:	Reentrant Syscalls
	`_mallinfo_r`:	mallinfo
	`_malloc_r`:	malloc
	`_malloc_stats_r`:	mallinfo
	`_malloc_usable_size_r`:	malloc
	`_mallopt_r`:	mallinfo
	`_mbsnrtowcs_r`:	mbsrtowcs
	`_mbsrtowcs_r`:	mbsrtowcs
	`_memalign_r`:	malloc
	`_mkdtemp_r`:	mktemp
	`_mkostemps_r`:	mktemp
	`_mkostemp_r`:	mktemp
	`_mkstemps_r`:	mktemp
	`_mkstemp_r`:	mktemp
	`_mktemp_r`:	mktemp
	`_open_r`:	Reentrant Syscalls
	`_perror_r`:	perror
	`_printf_r`:	sprintf
	`_putchar_r`:	putchar
	`_putc_r`:	putc
	`_putc_unlocked_r`:	putc_unlocked
	`_puts_r`:	puts
	`_putwchar_r`:	putwchar
	`_putwchar_unlocked_r`:	putwchar
	`_putwc_r`:	fputwc
	`_putwc_unlocked_r`:	fputwc
	`_raise_r`:	raise
	`_read_r`:	Reentrant Syscalls
	`_reallocf_r`:	malloc
	`_realloc_r`:	malloc
	`_reent`:	Reentrancy
	`_remove_r`:	remove
	`_rewind_r`:	rewind
	`_sbrk_r`:	Reentrant Syscalls
	`_scanf_r`:	sscanf
	`_setlocale_r`:	setlocale
	`_signal_r`:	signal
	`_siprintf_r`:	siprintf
	`_siscanf_r`:	siscanf
	`_sniprintf_r`:	siprintf
	`_snprintf_r`:	sprintf
	`_sprintf_r`:	sprintf
	`_sscanf_r`:	sscanf
	`_stat_r`:	Reentrant Syscalls
	`_strtod_r`:	strtod
	`_strtoll_r`:	strtoll
	`_strtol_r`:	strtol
	`_strtoull_r`:	strtoull
	`_strtoul_r`:	strtoul
	`_swprintf_r`:	swprintf
	`_swscanf_r`:	swscanf
	`_system_r`:	system
	`_tempnam_r`:	tmpnam
	`_tmpfile_r`:	tmpfile
	`_tmpnam_r`:	tmpnam
	`_tolower`:	tolower
	`_toupper`:	toupper
	`_tzset_r`:	tzset
	`_ungetc_r`:	ungetc
	`_ungetwc_r`:	ungetwc
	`_unlink_r`:	Reentrant Syscalls
	`_vasiprintf_r`:	viprintf
	`_vasniprintf_r`:	viprintf
	`_vasnprintf_r`:	vfprintf
	`_vasprintf_r`:	vfprintf
	`_vdiprintf_r`:	diprintf
	`_vdprintf_r`:	dprintf
	`_vfiprintf_r`:	viprintf
	`_vfiscanf_r`:	viscanf
	`_vfprintf_r`:	vfprintf
	`_vfscanf_r`:	vfscanf
	`_vfwprintf_r`:	vfwprintf
	`_vfwscanf`:	vfwscanf
	`_viprintf_r`:	viprintf
	`_viscanf_r`:	viscanf
	`_vprintf_r`:	vfprintf
	`_vscanf_r`:	vfscanf
	`_vsiprintf_r`:	viprintf
	`_vsiscanf_r`:	viscanf
	`_vsniprintf_r`:	viprintf
	`_vsnprintf_r`:	vfprintf
	`_vsprintf_r`:	vfprintf
	`_vsscanf_r`:	vfscanf
	`_vswprintf_r`:	vfwprintf
	`_vswscanf`:	vfwscanf
	`_vwprintf_r`:	vfwprintf
	`_vwscanf`:	vfwscanf
	`_wait_r`:	Reentrant Syscalls
	`_wcsdup_r`:	wcsdup
	`_wcsnrtombs_r`:	wcsrtombs
	`_wcsrtombs_r`:	wcsrtombs
	`_wcstod_r`:	wcstod
	`_wcstof_r`:	wcstod
	`_wcstoll_r`:	wcstoll
	`_wcstol_r`:	wcstol
	`_wcstoull_r`:	wcstoull
	`_wcstoul_r`:	wcstoul
	`_wprintf_r`:	swprintf
	`_write_r`:	Reentrant Syscalls
	`_wscanf_r`:	swscanf
	`__env_lock`:	__env_lock
	`__env_unlock`:	__env_lock
	`__fbufsize`:	stdio_ext
	`__flbf`:	stdio_ext
	`__fpending`:	stdio_ext
	`__fpurge`:	fpurge
	`__freadable`:	stdio_ext
	`__freading`:	stdio_ext
	`__fsetlocking`:	__fsetlocking
	`__fwritable`:	stdio_ext
	`__fwriting`:	stdio_ext
	`__malloc_lock`:	__malloc_lock
	`__malloc_unlock`:	__malloc_lock
	`__tz_lock`:	__tz_lock
	`__tz_unlock`:	__tz_lock

A
	`a64l`:	a64l
	`abort`:	abort
	`abs`:	abs
	`asctime`:	asctime
	`asiprintf`:	siprintf
	`asniprintf`:	siprintf
	`asnprintf`:	sprintf
	`asprintf`:	sprintf
	`assert`:	assert
	`atexit`:	atexit
	`atof`:	atof
	`atoff`:	atof
	`atoi`:	atoi
	`atol`:	atoi
	`atoll`:	atoll

B
	`bcmp`:	bcmp
	`bsearch`:	bsearch
	`bzero`:	bzero

C
	`calloc`:	calloc
	`clearerr`:	clearerr
	`clearerr_unlocked`:	clearerr
	`clock`:	clock
	`close`:	Stubs
	`ctime`:	ctime
	`ctime_r`:	ctime

D
	`difftime`:	difftime
	`diprintf`:	diprintf
	`div`:	div
	`dprintf`:	dprintf
	`drand48`:	rand48

E
	`ecvt`:	ecvt
	`ecvtbuf`:	ecvtbuf
	`ecvtf`:	ecvt
	`environ`:	getenv
	`environ`:	Stubs
	`erand48`:	rand48
	`errno` global vs macro:	Stubs
	`execve`:	Stubs
	`exit`:	exit
	extra argument, reentrant fns:	Reentrancy

F
	`fclose`:	fclose
	`fcloseall`:	fcloseall
	`fcvt`:	ecvt
	`fcvtbuf`:	ecvtbuf
	`fcvtf`:	ecvt
	`fdopen`:	fdopen
	`feof`:	feof
	`feof_unlocked`:	feof
	`ferror`:	ferror
	`ferror_unlocked`:	ferror
	`fflush`:	fflush
	`fflush_unlocked`:	fflush
	`ffs`:	ffs
	`fgetc`:	fgetc
	`fgetc_unlocked`:	fgetc
	`fgetpos`:	fgetpos
	`fgets`:	fgets
	`fgets_unlocked`:	fgets
	`fgetwc`:	fgetwc
	`fgetwc_unlocked`:	fgetwc
	`fgetws`:	fgetws
	`fgetws_unlocked`:	fgetws
	`fileno`:	fileno
	`fileno_unlocked`:	fileno
	`fiprintf`:	siprintf
	`fiscanf`:	siscanf
	`fmemopen`:	fmemopen
	`fopen`:	fopen
	`fopencookie`:	fopencookie
	`fork`:	Stubs
	`fprintf`:	sprintf
	`fpurge`:	fpurge
	`fputc`:	fputc
	`fputc_unlocked`:	fputc
	`fputs`:	fputs
	`fputs_unlocked`:	fputs
	`fputwc`:	fputwc
	`fputwc_unlocked`:	fputwc
	`fputws`:	fputws
	`fputws_unlocked`:	fputws
	`fread`:	fread
	`fread_unlocked`:	fread
	`free`:	malloc
	`freopen`:	freopen
	`fropen`:	funopen
	`fscanf`:	sscanf
	`fseek`:	fseek
	`fseeko`:	fseek
	`fsetpos`:	fsetpos
	`fstat`:	Stubs
	`ftell`:	ftell
	`ftello`:	ftell
	`funopen`:	funopen
	`fwide`:	fwide
	`fwopen`:	funopen
	`fwprintf`:	swprintf
	`fwrite`:	fwrite
	`fwrite_unlocked`:	fwrite
	`fwscanf`:	swscanf

G
	`gcvt`:	gvcvt
	`gcvtf`:	gvcvt
	`getc`:	getc
	`getchar`:	getchar
	`getchar_unlocked`:	getchar_unlocked
	`getc_unlocked`:	getc_unlocked
	`getdelim`:	getdelim
	`getenv`:	getenv
	`getline`:	getline
	`getpid`:	Stubs
	`gets`:	gets
	`getw`:	getw
	`getwc`:	fgetwc
	`getwchar`:	getwchar
	`getwchar_unlocked`:	getwchar
	`getwc_unlocked`:	fgetwc
	global reentrancy structure:	Reentrancy
	`gmtime`:	gmtime
	`gmtime_r`:	gmtime

I
	`index`:	index
	`iprintf`:	siprintf
	`isalnum`:	isalnum
	`isalpha`:	isalpha
	`isascii`:	isascii
	`isatty`:	Stubs
	`iscanf`:	siscanf
	`iscntrl`:	iscntrl
	`isdigit`:	isdigit
	`isgraph`:	isprint
	`islower`:	islower
	`isprint`:	isprint
	`ispunct`:	ispunct
	`isspace`:	isspace
	`isupper`:	isupper
	`iswalnum`:	iswalnum
	`iswalpha`:	iswalpha
	`iswblank`:	iswblank
	`iswcntrl`:	iswcntrl
	`iswctype`:	iswctype
	`iswdigit`:	iswdigit
	`iswgraph`:	iswgraph
	`iswlower`:	iswlower
	`iswprint`:	iswprint
	`iswpunct`:	iswpunct
	`iswspace`:	iswspace
	`iswupper`:	iswupper
	`iswxdigit`:	iswxdigit
	`isxdigit`:	isxdigit

J
	`jrand48`:	rand48

K
	`kill`:	Stubs

L
	`l64a`:	a64l
	`labs`:	labs
	`lcong48`:	rand48
	`ldiv`:	ldiv
	`link`:	Stubs
	linking the C library:	Syscalls
	list of reentrant functions:	Reentrancy
	`llabs`:	llabs
	`lldiv`:	lldiv
	`localeconv`:	setlocale
	`localtime`:	localtime
	`localtime_r`:	localtime
	`lrand48`:	rand48
	`lseek`:	Stubs

M
	`mallinfo`:	mallinfo
	`malloc`:	malloc
	`malloc_stats`:	mallinfo
	`malloc_usable_size`:	malloc
	`mallopt`:	mallinfo
	`mblen`:	mblen
	`mbsnrtowcs`:	mbsrtowcs
	`mbsrtowcs`:	mbsrtowcs
	`mbstowcs`:	mbstowcs
	`mbtowc`:	mbtowc
	`memalign`:	malloc
	`memchr`:	memchr
	`memcmp`:	memcmp
	`memmem`:	memmem
	`memmove`:	memmove
	`memset`:	memset
	`mkdtemp`:	mktemp
	`mkostemp`:	mktemp
	`mkostemps`:	mktemp
	`mkstemp`:	mktemp
	`mkstemps`:	mktemp
	`mktemp`:	mktemp
	`mktime`:	mktime
	`mrand48`:	rand48

N
	`nrand48`:	rand48

O
	`on_exit`:	on_exit
	`open`:	Stubs
	`open_memstream`:	open_memstream
	`open_wmemstream`:	open_memstream
	OS interface subroutines:	Stubs

P
	`perror`:	perror
	`printf`:	sprintf
	`psignal`:	psignal
	`putc`:	putc
	`putchar`:	putchar
	`putchar_unlocked`:	putchar_unlocked
	`putc_unlocked`:	putc_unlocked
	`puts`:	puts
	`putw`:	putw
	`putwc`:	fputwc
	`putwchar`:	putwchar
	`putwchar_unlocked`:	putwchar
	`putwc_unlocked`:	fputwc

Q
	`qsort`:	qsort

R
	`raise`:	raise
	`rand`:	rand
	`rand48`:	rand48
	`rand_r`:	rand
	`read`:	Stubs
	`realloc`:	malloc
	`reallocf`:	malloc
	`reent.h`:	Reentrancy
	reentrancy:	Reentrancy
	reentrancy structure:	Reentrancy
	reentrant function list:	Reentrancy
	`remove`:	remove
	`rename`:	rename
	`rewind`:	rewind
	`rindex`:	rindex

S
	`sbrk`:	Stubs
	`scanf`:	sscanf
	`seed48`:	rand48
	`setbuf`:	setbuf
	`setbuffer`:	setbuffer
	`setlinebuf`:	setlinebuf
	`setlocale`:	setlocale
	`setvbuf`:	setvbuf
	`signal`:	signal
	`siprintf`:	siprintf
	`siscanf`:	siscanf
	`sniprintf`:	siprintf
	`snprintf`:	sprintf
	`sprintf`:	sprintf
	`srand`:	rand
	`srand48`:	rand48
	`sscanf`:	sscanf
	`stat`:	Stubs
	`stpcpy`:	stpcpy
	`stpncpy`:	stpncpy
	`strcasecmp`:	strcasecmp
	`strcasestr`:	strcasestr
	`strcat`:	strcat
	`strchr`:	strchr
	`strcmp`:	strcmp
	`strcoll`:	strcoll
	`strcpy`:	strcpy
	`strcspn`:	strcspn
	`strerror`:	strerror
	`strerror_r`:	strerror_r
	`strftime`:	strftime
	`strlen`:	strlen
	`strlwr`:	strlwr
	`strncasecmp`:	strncasecmp
	`strncat`:	strncat
	`strncmp`:	strncmp
	`strncpy`:	strncpy
	`strnlen`:	strnlen
	`strpbrk`:	strpbrk
	`strrchr`:	strrchr
	`strsep`:	strtok
	`strsignal`:	strsignal
	`strspn`:	strspn
	`strstr`:	strstr
	`strtod`:	strtod
	`strtof`:	strtod
	`strtok`:	strtok
	`strtok_r`:	strtok
	`strtol`:	strtol
	`strtoll`:	strtoll
	`strtoul`:	strtoul
	`strtoull`:	strtoull
	`strupr`:	strupr
	`strxfrm`:	strxfrm
	stubs:	Stubs
	subroutines for OS interface:	Stubs
	`swprintf`:	swprintf
	`swscanf`:	swscanf
	`system`:	system

T
	`tempnam`:	tmpnam
	`time`:	time
	`times`:	Stubs
	`tmpfile`:	tmpfile
	`tmpnam`:	tmpnam
	`toascii`:	toascii
	`tolower`:	tolower
	`toupper`:	toupper
	`towctrans`:	towctrans
	`towlower`:	towlower
	`towupper`:	towupper
	`tzset`:	tzset

U
	`unctrl`:	unctrl
	`unctrllen`:	unctrl
	`ungetc`:	ungetc
	`ungetwc`:	ungetwc
	`unlink`:	Stubs

V
	`vasiprintf`:	viprintf
	`vasniprintf`:	viprintf
	`vasnprintf`:	vfprintf
	`vasprintf`:	vfprintf
	`va_alist`:	va_alist
	`va_arg`:	va_arg
	`va_arg`:	va_arg-trad
	`va_dcl`:	va_alist
	`va_end`:	va_end
	`va_end`:	va_end-trad
	`va_start`:	va_start
	`va_start`:	va_start-trad
	`vdiprintf`:	diprintf
	`vdprintf`:	dprintf
	`vfiprintf`:	viprintf
	`vfiscanf`:	viscanf
	`vfprintf`:	vfprintf
	`vfscanf`:	vfscanf
	`vfwprintf`:	vfwprintf
	`vfwscanf`:	vfwscanf
	`viprintf`:	viprintf
	`viscanf`:	viscanf
	`vprintf`:	vfprintf
	`vscanf`:	vfscanf
	`vsiprintf`:	viprintf
	`vsiscanf`:	viscanf
	`vsniprintf`:	viprintf
	`vsnprintf`:	vfprintf
	`vsprintf`:	vfprintf
	`vsscanf`:	vfscanf
	`vswprintf`:	vfwprintf
	`vswscanf`:	vfwscanf
	`vwprintf`:	vfwprintf
	`vwscanf`:	vfwscanf

W
	`wait`:	Stubs
	`wcscasecmp`:	wcscasecmp
	`wcscat`:	wcscat
	`wcscoll`:	wcscoll
	`wcsdup`:	wcsdup
	`wcsftime`:	wcsftime
	`wcsncasecmp`:	wcsncasecmp
	`wcsnlen`:	wcsnlen
	`wcsnrtombs`:	wcsrtombs
	`wcsrtombs`:	wcsrtombs
	`wcstod`:	wcstod
	`wcstof`:	wcstod
	`wcstok`:	wcstok
	`wcstol`:	wcstol
	`wcstoll`:	wcstoll
	`wcstombs`:	wcstombs
	`wcstoul`:	wcstoul
	`wcstoull`:	wcstoull
	`wcswidth`:	wcswidth
	`wcsxfrm`:	wcsxfrm
	`wctomb`:	wctomb
	`wctrans`:	wctrans
	`wctype`:	wctype
	`wcwidth`:	wcwidth
	`wprintf`:	swprintf
	`write`:	Stubs
	`wscanf`:	swscanf

Jump to:	_ A B C D E F G I J K L M N O P Q R S T U V W

1 Introduction
2 Standard Utility Functions (stdlib.h)
3 Character Type Macros and Functions (ctype.h)
4 Input and Output (stdio.h)
5 Strings and Memory (string.h)
6 Wide Character Strings (wchar.h)
7 Signal Handling (signal.h)
8 Time Functions (time.h)
9 Locale (locale.h)
- 9.1 setlocale, localeconv—select or query locale
10 Reentrancy
11 Miscellaneous Macros and Functions
- 11.1 ffs—find first bit set in a word
- 11.2 unctrl—get printable representation of a character
12 System Calls
- 12.1 Definitions for OS interface
- 12.2 Reentrant covers for OS subroutines
13 Variable Argument Lists
- 13.1 ANSI-standard macros, stdarg.h
- 13.2 Traditional macros, varargs.h
Document Index

• psignal:		Print a signal message to standard error
• raise:		Send a signal
• signal:		Specify handler subroutine for a signal

• ffs:		Return first bit set in a word
• unctrl:		Return printable representation of a character

• va_alist:
• va_start-trad:
• va_arg-trad:
• va_end-trad:

• Stubs:		Definitions for OS interface
• Reentrant Syscalls:		Reentrant covers for OS subroutines

• Stdarg:
• Varargs:

• va_start:
• va_arg:
• va_end:

The Red Hat newlib C Library

1 Introduction

2 Standard Utility Functions (stdlib.h)

2.1 _Exit—end program execution with no cleanup processing

2.2 a64l, l64a—convert between radix-64 ASCII string and long

2.3 abort—abnormal termination of a program

2.4 abs—integer absolute value (magnitude)

2.5 assert—macro for debugging diagnostics

2.6 atexit—request execution of functions at program exit

2.7 atof, atoff—string to double or float

2.8 atoi, atol—string to integer

2.9 atoll—convert a string to a long long integer

2.10 bsearch—binary search

2.11 calloc—allocate space for arrays

2.12 div—divide two integers

2.13 ecvt, ecvtf, fcvt, fcvtf—double or float to string

2.14 gvcvt, gcvtf—format double or float as string

2.15 ecvtbuf, fcvtbuf—double or float to string

2.16 __env_lock, __env_unlock—lock environ variable

2.17 exit—end program execution

2.18 getenv—look up environment variable

2.19 labs—long integer absolute value

2.20 ldiv—divide two long integers

2.21 llabs—compute the absolute value of an long long integer.

2.22 lldiv—divide two long long integers

2.23 malloc, realloc, free—manage memory

2.24 mallinfo, malloc_stats, mallopt—malloc support

2.25 __malloc_lock, __malloc_unlock—lock malloc pool

2.26 mblen—minimal multibyte length function

2.27 mbsrtowcs, mbsnrtowcs—convert a character string to a wide-character string

2.28 mbstowcs—minimal multibyte string to wide char converter

2.29 mbtowc—minimal multibyte to wide char converter

2.30 on_exit—request execution of function with argument at program exit

2.31 qsort—sort an array

2.32 rand, srand—pseudo-random numbers

2.33 rand48, drand48, erand48, lrand48, nrand48, mrand48, jrand48, srand48, seed48, lcong48—pseudo-random number generators and initialization routines

2.34 strtod, strtof—string to double or float

2.35 strtol—string to long

2.36 strtoll—string to long long

2.37 strtoul—string to unsigned long

2.38 strtoull—string to unsigned long long

2.39 wcsrtombs, wcsnrtombs—convert a wide-character string to a character string

2.40 wcstod, wcstof—wide char string to double or float

2.41 wcstol—wide string to long

2.42 wcstoll—wide string to long long

2.43 wcstoul—wide string to unsigned long

2.44 wcstoull—wide string to unsigned long long

2.45 system—execute command string

2.46 wcstombs—minimal wide char string to multibyte string converter

2.47 wctomb—minimal wide char to multibyte converter

3 Character Type Macros and Functions (ctype.h)

3.1 isalnum—alphanumeric character predicate

3.2 isalpha—alphabetic character predicate

3.3 isascii—ASCII character predicate

3.4 iscntrl—control character predicate

3.5 isdigit—decimal digit predicate

3.6 islower—lowercase character predicate

3.7 isprint, isgraph—printable character predicates

3.8 ispunct—punctuation character predicate

3.9 isspace—whitespace character predicate

3.10 isupper—uppercase character predicate

3.11 isxdigit—hexadecimal digit predicate

3.12 toascii—force integers to ASCII range

3.13 tolower—translate characters to lowercase

3.14 toupper—translate characters to uppercase

3.15 iswalnum—alphanumeric wide character test

3.16 iswalpha—alphabetic wide character test

3.17 iswcntrl—control wide character test

3.18 iswblank—blank wide character test

3.19 iswdigit—decimal digit wide character test

3.20 iswgraph—graphic wide character test

3.21 iswlower—lowercase wide character test

3.22 iswprint—printable wide character test

3.23 iswpunct—punctuation wide character test

3.24 iswspace—whitespace wide character test

3.25 iswupper—uppercase wide character test

3.26 iswxdigit—hexadecimal digit wide character test

3.27 iswctype—extensible wide-character test

3.28 wctype—get wide-character classification type

3.29 towlower—translate wide characters to lowercase

2 Standard Utility Functions (`stdlib.h`)

2.1 `_Exit`—end program execution with no cleanup processing

2.2 `a64l`, `l64a`—convert between radix-64 ASCII string and long

2.3 `abort`—abnormal termination of a program

2.4 `abs`—integer absolute value (magnitude)

2.5 `assert`—macro for debugging diagnostics

2.6 `atexit`—request execution of functions at program exit

2.7 `atof`, `atoff`—string to double or float

2.8 `atoi`, `atol`—string to integer

2.9 `atoll`—convert a string to a long long integer

2.10 `bsearch`—binary search

2.11 `calloc`—allocate space for arrays

2.12 `div`—divide two integers

2.13 `ecvt`, `ecvtf`, `fcvt`, `fcvtf`—double or float to string

2.14 `gvcvt`, `gcvtf`—format double or float as string

2.15 `ecvtbuf`, `fcvtbuf`—double or float to string

2.16 `__env_lock`, `__env_unlock`—lock environ variable

2.17 `exit`—end program execution

2.18 `getenv`—look up environment variable

2.19 `labs`—long integer absolute value

2.20 `ldiv`—divide two long integers

2.21 `llabs`—compute the absolute value of an long long integer.

2.22 `lldiv`—divide two long long integers

2.23 `malloc`, `realloc`, `free`—manage memory

2.24 `mallinfo`, `malloc_stats`, `mallopt`—malloc support

2.25 `__malloc_lock`, `__malloc_unlock`—lock malloc pool

2.26 `mblen`—minimal multibyte length function

2.27 `mbsrtowcs`, `mbsnrtowcs`—convert a character string to a wide-character string

2.28 `mbstowcs`—minimal multibyte string to wide char converter

2.29 `mbtowc`—minimal multibyte to wide char converter

2.30 `on_exit`—request execution of function with argument at program exit

2.31 `qsort`—sort an array

2.32 `rand`, `srand`—pseudo-random numbers

2.33 `rand48`, `drand48`, `erand48`, `lrand48`, `nrand48`, `mrand48`, `jrand48`, `srand48`, `seed48`, `lcong48`—pseudo-random number generators and initialization routines

2.34 `strtod`, `strtof`—string to double or float

2.35 `strtol`—string to long

2.36 `strtoll`—string to long long

2.37 `strtoul`—string to unsigned long

2.38 `strtoull`—string to unsigned long long

2.39 `wcsrtombs`, `wcsnrtombs`—convert a wide-character string to a character string

2.40 `wcstod`, `wcstof`—wide char string to double or float

2.41 `wcstol`—wide string to long

2.42 `wcstoll`—wide string to long long

2.43 `wcstoul`—wide string to unsigned long

2.44 `wcstoull`—wide string to unsigned long long

2.45 `system`—execute command string

2.46 `wcstombs`—minimal wide char string to multibyte string converter

2.47 `wctomb`—minimal wide char to multibyte converter

3 Character Type Macros and Functions (`ctype.h`)

3.1 `isalnum`—alphanumeric character predicate

3.2 `isalpha`—alphabetic character predicate

3.3 `isascii`—ASCII character predicate

3.4 `iscntrl`—control character predicate

3.5 `isdigit`—decimal digit predicate

3.6 `islower`—lowercase character predicate

3.7 `isprint`, `isgraph`—printable character predicates

3.8 `ispunct`—punctuation character predicate

3.9 `isspace`—whitespace character predicate

3.10 `isupper`—uppercase character predicate

3.11 `isxdigit`—hexadecimal digit predicate

3.12 `toascii`—force integers to ASCII range

3.13 `tolower`—translate characters to lowercase

3.14 `toupper`—translate characters to uppercase

3.15 `iswalnum`—alphanumeric wide character test

3.16 `iswalpha`—alphabetic wide character test

3.17 `iswcntrl`—control wide character test

3.18 `iswblank`—blank wide character test

3.19 `iswdigit`—decimal digit wide character test

3.20 `iswgraph`—graphic wide character test

3.21 `iswlower`—lowercase wide character test

3.22 `iswprint`—printable wide character test

3.23 `iswpunct`—punctuation wide character test

3.24 `iswspace`—whitespace wide character test

3.25 `iswupper`—uppercase wide character test

3.26 `iswxdigit`—hexadecimal digit wide character test

3.27 `iswctype`—extensible wide-character test

3.28 `wctype`—get wide-character classification type

3.29 `towlower`—translate wide characters to lowercase

3.30 `towupper`—translate wide characters to uppercase

3.31 `towctrans`—extensible wide-character translation