C Library - <stdlib.h>

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The stdlib.h header defines four variable types, several macros, and various functions for performing general functions.

Library Variables

Following are the variable types defined in the header stdlib.h −

Sr.No. Variable & Description
1

size_t

This is the unsigned integral type and is the result of the sizeof keyword.
2

wchar_t

This is an integer type of the size of a wide character constant.
3

div_t

This is the structure returned by the div function.
4

ldiv_t

This is the structure returned by the ldiv function.

Library Macros

Following are the macros defined in the header stdlib.h −

Sr.No. Macro & Description
1

NULL

This macro is the value of a null pointer constant.
2

EXIT_FAILURE

This is the value for the exit function to return in case of failure.
3

EXIT_SUCCESS

This is the value for the exit function to return in case of success.
4

RAND_MAX

This macro is the maximum value returned by the rand function.
5

MB_CUR_MAX

This macro is the maximum number of bytes in a multi-byte character set which cannot be larger than MB_LEN_MAX.

Library Functions

Following are the functions defined in the header stlib.h −

Sr.No. Function & Description
1 double atof(const char *str)

Converts the string pointed to, by the argument str to a floating-point number (type double).
2 int atoi(const char *str)

Converts the string pointed to, by the argument str to an integer (type int).
3 long int atol(const char *str)

Converts the string pointed to, by the argument str to a long integer (type long int).
4 double strtod(const char *str, char **endptr)

Converts the string pointed to, by the argument str to a floating-point number (type double).
5 long int strtol(const char *str, char **endptr, int base)

Converts the string pointed to, by the argument str to a long integer (type long int).
6 unsigned long int strtoul(const char *str, char **endptr, int base)

Converts the string pointed to, by the argument str to an unsigned long integer (type unsigned long int).
7 void *calloc(size_t nitems, size_t size)

Allocates the requested memory and returns a pointer to it.
8 void free(void *ptr

Deallocates the memory previously allocated by a call to calloc, malloc, or realloc.
9 void *malloc(size_t size)

Allocates the requested memory and returns a pointer to it.
10 void *realloc(void *ptr, size_t size)

Attempts to resize the memory block pointed to by ptr that was previously allocated with a call to malloc or calloc.
11 void abort(void)

Causes an abnormal program termination.
12 int atexit(void (*func)(void))

Causes the specified function func to be called when the program terminates normally.
13 void exit(int status)

Causes the program to terminate normally.
14 char *getenv(const char *name)

Searches for the environment string pointed to by name and returns the associated value to the string.
15 int system(const char *string)

The command specified by string is passed to the host environment to be executed by the command processor.
16 void *bsearch(const void *key, const void *base, size_t nitems, size_t size, int (*compar)(const void *, const void *))

Performs a binary search.
17 void qsort(void *base, size_t nitems, size_t size, int (*compar)(const void *, const void*))

Sorts an array.
18 int abs(int x)

Returns the absolute value of x.
19 div_t div(int numer, int denom)

Divides numer (numerator) by denom (denominator).
20 long int labs(long int x)

Returns the absolute value of x.
21 ldiv_t ldiv(long int numer, long int denom)

Divides numer (numerator) by denom (denominator).
22 int rand(void)

Returns a pseudo-random number in the range of 0 to RAND_MAX.
23 void srand(unsigned int seed)

This function seeds the random number generator used by the function rand.
24 int mblen(const char *str, size_t n)

Returns the length of a multibyte character pointed to by the argument str.
25 size_t mbstowcs(schar_t *pwcs, const char *str, size_t n)

Converts the string of multibyte characters pointed to by the argument str to the array pointed to by pwcs.
26 int mbtowc(whcar_t *pwc, const char *str, size_t n)

Examines the multibyte character pointed to by the argument str.
27 size_t wcstombs(char *str, const wchar_t *pwcs, size_t n)

Converts the codes stored in the array pwcs to multibyte characters and stores them in the string str.
28 int wctomb(char *str, wchar_t wchar)

Examines the code which corresponds to a multibyte character given by the argument wchar.
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