C Programming/Standard library reference

Headers

ANSI C (C89)/ISO C (C90)

assert.h	Verify program assertion file
ctype.h	Character types file.
errno.h	System error numbers file
float.h	Floating types file
limits.h	Implementation-defined constants file.
locale.h	Category macros file.
math.h	Mathematical declarations file.
setjmp.h	Stack environment declarations file.
signal.h	Signals file.
stdarg.h	Handle variable argument list file.
stddef.h	Standard type definitions file.
stdio.h	Standard buffered input/output file.
stdlib.h	Standard library definitions file.
string.h	String operations file.
time.h	Time types file.

ISO C (C94/C95), Amendment 1 (AMD1)

Very old compilers may not include some or all of these headers

iso646.h	Alternative spellings.
wchar.h	Wide-character handling.
wctype.h	Wide-character classification and mapping utilities.

ISO C (C99)

These are supported only in newer compilers

complex.h	Complex arithmetic.
fenv.h	Floating-point environment.
inttypes.h	Fixed size integer types.
stdbool.h	Boolean type and values.
stdint.h	Integer types.
tgmath.h	Type-generic macros.

ISO C (C11)

These are supported only in newer compilers

stdalign.h	Alignment keywords and macros.
stdatomic.h	Atomic operations on data shared between threads.
stdnoreturn.h	_Noreturn function specifier macro.
threads.h	Support for multiple threads of execution.
uchar.h	Types and functions for manipulating Unicode characters.

Table of functions

This table also includes function-like macros

assert.h

assert

complex.h

cacos cacosf cacosl casin casinf casinl catan catanf

catanl ccos ccosf ccosl csin csinf csinl ctan

ctanf ctanl cacosh cacoshf cacoshl casinh casinhf casinhl

catanh catanhf catanhl ccosh ccoshf ccoshl csinh csinhf

csinhl ctanh ctanhf ctanhl cexp cexpf cexpl clog

clogf clogl cabs cabsf cabsl cpow cpowf cpowl

csqrt csqrtf csqrtl carg cargf cargl cimag cimagf

cimagl conj conjf conjl cproj cprojf cprojl creal

crealf creall

ctype.h

isalnum isalpha isblank iscntrl

isdigit isgraph islower isprint

ispunct isspace isupper isxdigit

tolower toupper

fenv.h

feclearexcept fegetenv fegetexceptflag fegetround

feholdexcept feraiseexcept fesetenv fesetexceptflag

fesetround fetestexcept feupdateenv

inttypes.h

imaxabs imaxdiv strtoimax strtoumax

wcstoimax wcstoumax

locale.h

localeconv setlocale

math.h

fpclassify isfinite isgreater isgreaterequal

isinf isless islessequal islessgreater

isnan isnormal isunordered signbit

setjmp.h

longjmp setjmp

signal.h

raise

stdarg.h

va_arg va_copy va_end va_start

stdatomic.h

atomic_init atomic_thread_fence atomic_signal_fence atomic_is_lock_free atomic_store atomic_store_explicit atomic_load atomic_load_explicit

atomic_exchange atomic_exchange_explicit atomic_compare_exchange_strong atomic_compare_exchange_strong_explicit atomic_compare_exchange_weak atomic_compare_exchange_weak_explicit atomic_fetch atomic_fetch_key_explicit

atomic_flag_test_and_set atomic_flag_test_and_set_explicit atomic_flag_clear atomic_flag_clear_explicit

stddef.h

offsetof

stdio.h

clearerr fclose feof fgetc fgetpos fgets fopen fprintf fputs

fread fscanf fseek fsetpos ftell fwprintf fwrite getc getchar

gets perror printf putc putchar puts remove rename rewind

scanf setbuf setvbuf sprintf tmpfile ungetc vwprintf wprintf wscanf

stdlib.h

abort abs labs atexit

atof atoi atol bsearch

div ldiv exit free

getenv malloc calloc realloc

qsort rand srand strtod

strtol strtoul system

string.h

memchr memcmp memcpy memmove

memset strcat strncat strchr

strcmp strncmp strcoll strcpy

strncpy strcspn strerror strlen

strpbrk strrchr strspn strstr

strtok strxfrm

threads.h

call_once cnd_broadcast cnd_destroy cnd_init cnd_signal cnd_timedwait cnd_wait mtx_destroy

mtx_init mtx_lock mtx_timedlock mtx_trylock mtx_unlock thrd_create thrd_current thrd_detach

thrd_equal thrd_exit thrd_join thrd_sleep thrd_yield tss_create tss_delete tss_get

tss_set

time.h

asctime clock ctime difftime

gmtime localtime mktime strftime

time

uchar.h

mbrtoc16 c16rtomb mbrtoc32 c32rtomb

wchar.h

btowc fgetwc fgetws fputwc fwide fwprintf fwscanf getwc

getwchar mbrlen mbrtowc mbsinit mbsrtowcs putwc putwchar swprintf

swscanf ungetwc vfwprintf vswprintf vwprintf wcrtomb wcscat wcschr

wcscmp wcscoll wcscpy wcscspn wcsftime wcslen wcsncat wcsncmp

wcsncpy wcspbrk wcsrchr wcsrtombs wcsspn wcsstr wcstod wcstok

wcstol wcstoul wcsxfrm wctob wmemchr wmemcmp wmemcpy wmemmove

wmemset wprintf wscanf

wctype.h

iswalnum iswalpha iswcntrl iswctype

iswdigit iswgraph iswlower iswprint

iswpunct iswspace iswupper iswxdigit

towctrans towlower towupper wctrans

wctype