C Standard Library

C Standard Library

C - <stdlib.h>

The C <stdlib.h> header defines several general purpose functions which includes dynamic memory management, random number generation, communication with the environment, integer arithmetics, searching, sorting and converting.

Library Functions

Numeric string conversion functions

Functions	Description
atof()	Convert string to double.
atoi()	Converts a byte string to an integer value.
atol()	Converts a byte string to a long integer value.
atoll()	Converts a byte string to a long long integer value.
strtod()	Converts string to double.
strtof()	Converts string to float.
strtol()	Convert string to long integer.
strtold()	Converts string to long double.
strtoll()	Convert string to long long integer.
strtoul()	Convert string to unsigned long integer.
strtoull()	Convert string to unsigned long long integer.

Dynamic memory management functions

Functions	Description
calloc()	Allocate and zero-initialize array.
free()	Deallocates previously allocated memory.
malloc()	Allocates memory.
realloc()	Reallocates previously allocated memory block.

Pseudo-random sequence generation functions

Functions	Description
rand()	Returns a pseudo-random integral value between 0 and RAND_MAX.
srand()	Seeds the pseudo-random number generator used by rand() with the value seed.

Environment functions

Functions	Description
abort()	Aborts the current process.
getenv()	Gets environment string.

Integer arithmetics functions

Functions	Description
abs()	Returns absolute value of an integral value.
div()	Returns quotient and remainder of integer division.
labs()	Returns absolute value of an integral value.
ldiv()	Returns quotient and remainder of integer division.
llabs()	Returns absolute value of an integral value.
lldiv()	Returns quotient and remainder of integer division.

Multibyte/wide character conversions

Functions	Description
mblen()	Returns the number of bytes in the next multibyte character.
mbtowc()	Converts the next multibyte character to wide character.
wctomb()	Converts a wide character to its multibyte representation.

Library Types

Types	Description
div_t	Structure type, return by div() function.
ldiv_t	Structure type, return by ldiv() function.
lldiv_t	Structure type, return by lldiv() function.
size_t	Unsigned integer type.

Library Macros

Macro constants

Macros	Description
EXIT_FAILURE	Program failure termination code.
EXIT_SUCCESS	Program success termination code.
MB_CUR_MAX	Maximum size of a multibyte characters with the current locale.
NULL	Null pointer.
RAND_MAX	Maximum value returned by rand() function.

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