STANDARD UTILITY FUNCTIONS (stdlib.h)
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, atoff [string to double or float]
atoi, atol [string to integer]
bsearch [binary search]
calloc [allocate space for arrays]
div [divide two integers]
ecvt, ecvtf, fcvt, fcvtf [double or float to string]
gvcvt, gcvtf [format double or float as string]
ecvtbuf, fcvtbuf [double or float to string]
exit [end program execution]
getenv [look up environment variable]
labs [long integer absolute value]
ldiv [divide two long integers]
malloc, realloc, free [manage memory]
mmbtowc [minimal multibyte to wide char converter]
qsort [sort an array]
rand, srand [pseudo-random numbers]
strtod, strtodf [string to double or float]
strtol [string to long]
strtoul [string to unsigned long]
system [execute command string]
wctomb [minimal wide char to multibyte converter]
CHARACTER TYPE MACROS AND FUNCTIONS (ctype.h)
isalnum [alphanumeric character predicate]
isalpha [alphabetic character predicate]
isascii [ASCII character predicate]
iscntrl [control character predicate]
isdigit [decimal digit predicate]
islower [lower-case character predicate]
isprint, isgraph [printable character predicates]
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 lower case]
toupper [translate characters to upper case]
INPUT AND OUTPUT (stdio.h)
clearerr [clear file or stream error indicator]
fclose [close a file]
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]
fiprintf [format output to file (integer only)]
fopen [open a file]
fdopen [turn open file into a stream]
fputc [write a character on a stream or file]
fputs [write a character string in a file or stream]
fread [read array elements from a file]
freopen [open a file using an existing file descriptor]
fseek [set file position]
fsetpos [restore position of a stream or file]
ftell [return position in a stream or file]
fwrite [write array elements]
getc [read a character (macro)]
getchar [read a character (macro)]
gets [get character string]
iprintf [write formatted output (integer only)]
mktemp, mkstemp [generate unused file name]
perror [print an error message on standard error]
putc [write a character (macro)]
putchar [write a character (macro)]
puts [write a character string]
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]
setvbuf [specify file or stream buffering]
siprintf [write formatted output (integer only)]
printf, fprintf, sprintf [format output]
scanf, fscanf, sscanf [scan and format input]
tmpfile [create a temporary file]
tmpnam, tempnam [name for a temporary file]
vprintf, vfprintf, vsprintf [format argument list]
STRINGS AND MEMORY (string.h)
bcmp [compare two memory areas]
bcopy [copy memory regions]
bzero [initialize memory to zero]
index [search for character in string]
memchr [find character in memory]
memcmp [compare two memory areas]
memcpy [copy memory regions]
memmove [move possibly overlapping memory]
memset [set an area of memory]
rindex [reverse search for character in string]
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]
trlen [character string length]
strncat [concatenate strings]
strncmp [character string compare]
strncpy [counted copy string]
strpbrk [find chars in string]
strrchr [reverse search for character in string]
strspn [find initial match]
strstr [find string segment]
strtok [get next token from a string]
strxfrm [transform string]
SIGNAL HANDLING (signal.h)
raise [send a signal]
signal [specify handler subroutine for a signal]
TIME FUNCTIONS (time.h)
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 traditional form]
localtime [convert time to local representation]
mktime [convert time to arithmetic representation]
strftime [flexible calendar time formatter]
time [get current calendar time (as single number)]
LOCALE (Locale.h)
setlocale, localeconv [select or query locale]
MISCELLANEOUS MACROS AND FUNCTIONS
unctrl [translate characters to upper case]
REENTRANT COVERS FOR OS SUBROUTINES
ANSI-STANDARD MACROS, (stdarg.h)
va_start [initialize variable argument list]
va_arg [extract a value from argument list]
va_end [abandon a variable argument list]
TRADITIONAL MACROS (varargs.h)
va_dcl [declare variable arguments]
va_start [initialize variable argument list]
va_arg [extract a value from argument list]
va_end [abandon a variable argument list]