# stdlib.h ## **Overview** **Related Modules:** [UTILS](UTILS.md) **Description:** Declares common functions used for performing I/O operations. You can use the functions provided in this file to complete string conversion, random number generation, array sorting, and tree-related operations during development. **Since:** 1.0 **Version:** 1.0 ## **Summary** ## Data Structures

Data Structure Name

Description

div_t

Defines the structures of the division operation result.

ldiv_t

Defines the structures of the division operation result.

lldiv_t

Defines the structures of the division operation result.

## Functions

Function Name

Description

atoi (const char *nptr)

int 

Converts an input string to an integer.

atol (const char *nptr)

long 

Converts an input string to a long integer.

atoll (const char *nptr)

long long 

Converts a string to an 8-byte long integer.

atof (const char *nptr)

double 

Converts an input string to a double-precision floating-point number.

strtof (const char *nptr, char **endptr)

float 

Converts an input string to a floating-point number.

strtod (const char *nptr, char **endptr)

double 

Converts a string to double.

strtold (const char *nptr, char **endptr)

long double 

Converts a string to long double.

strtol (const char *nptr, char **endptr, int base)

long 

Converts a string to a long integer according to the given base.

strtoul (const char *nptr, char **endptr, int base)

unsigned long 

Converts a string to an unsigned long integer according to the given base.

strtoll (const char *nptr, char **endptr, int base)

long long 

Converts a string to a long long integer according to the given base.

strtoull (const char *nptr, char **endptr, int base)

unsigned long long 

Converts a string to an unsigned long long integer according to the given base.

rand (void)

int 

Generates a pseudo-random number.

srand (unsigned int seed)

void 

Initializes a random number generator.

malloc (size_t size)

void * 

Dynamically allocates a memory block of size.

calloc (size_t nmemb, size_t size)

void * 

Dynamically allocates nmemb memory blocks of size.

realloc (void *ptr, size_t size)

void * 

Changes the size of the memory block pointed to by ptr to size bytes.

free (void *ptr)

void 

Releases the memory space pointed to by ptr.

abort (void)

_Noreturn void 

Terminates an abnormal process and sends the SIGABRT signal to the caller.

atexit (void(*func)(void))

int 

Registers a termination function.

exit (int status)

void 

Terminates the calling process, clears the used memory space and various data structures in the kernel, and sends the process end status to the parent process. All functions registered with atexit and on_exit are called in the reverse order.

getenv (const char *name)

char * 

Obtains the value of an environment variable.

_Exit (int status)

void 

Terminates the calling process, clears the used memory space and various data structures in the kernel, and sends the process end status to the parent process.

assert (scalar expression)

void 

Aborts the program if assertion is false.

secure_getenv (const char *name)

char * 

Obtains the value of an environment variable.

bsearch (const void *key, const void *base, size_t nel, size_t width, int(*compar)(const void *, const void *))

void * 

Searches for key using the binary search algorithm from the array element base[0] to base[num-1].

qsort (const void *base, size_t nel, size_t width, int(*compar)(const void *, const void *))

void 

Sorts array elements base[0] to base[num-1] based on the comparison rules of compar.

abs (int i)

int 

Obtains the absolute value of an integer value.

labs (long i)

long 

Calculates the absolute value of a long integer.

llabs (long long i)

long long 

Calculates the absolute value of a long long integer.

div (int numerator, int denominator)

div_t 

Calculates the quotient and remainder of an integer after division.

ldiv (long numerator, long denominator)

ldiv_t 

Calculates the quotient and remainder of a long integer after division.

lldiv (long long numerator, long long denominator)

lldiv_t 

Calculates the quotient and remainder of a long long integer after division.

mblen (const char *s, size_t n)

int 

Obtains the number of bytes in the next multi-byte string.

mbtowc (wchar_t *pwc, const char *s, size_t n)

int 

Converts a string constant to a wide character.

wctomb (char *s, wchar_t wc)

int 

Converts a wide character to its multi-byte sequence and stores it in a character array.

mbstowcs (wchar_t *dest, const char *src, size_t n)

size_t 

Converts a multi-byte string to a wide-character string.

wcstombs (char *dest, const wchar_t *src, size_t n)

size_t 

Converts a wide-character string to a multi-byte string.

posix_memalign (void **memptr, size_t alignment, size_t size)

int 

Allocates memory with the specified size based on the given alignment.

setenv (const char *name, const char *value, int overwrite)

int 

Add or change an environment variable.

unsetenv (const char *name)

int 

Deletes an environment variable.

mkstemp (char *template)

int 

Creates and opens a unique temporary file.

mkostemp (char *template, int flags)

int 

Creates and opens a unique temporary file.

mkdtemp (char *template)

char * 

Creates a unique temporary directory based on template.

getsubopt (char **optionp, char *const *tokens, char **valuep)

int 

Processes the parameters of an option in the command line.

rand_r (unsigned *seedp)

int 

Generates a pseudo-random number.

realpath (const char *__restrict path, char *__restrict resolved)

char * 

Obtains a normalized absolute path.

random (void)

long int 

Generates a pseudo-random number.

srandom (unsigned int seed)

void 

Initializes a random number generator.

initstate (unsigned int seed, char *state, size_t n)

char * 

Initializes a random number generator.

setstate (char *state)

char * 

Sets the current state list for subsequent random use.

putenv (char *s)

int 

Configures an environment variable.

unlockpt (int fd)

int 

Unlocks the secondary pseudo terminal corresponding to a primary pseudo terminal.

ptsname (int fd)

char * 

Obtains the name of a pseudo terminal.

l64a (long value)

char * 

Converts a long integer to a 64-bit ASCII string.

a64l (const char *str64)

long 

Converts between a 32-bit long integer and a little-endian 64-bit ASCII string.

drand48 (void)

double 

Obtains a random number.

erand48 (unsigned short xsubi[3])

double 

Obtains a random number.

lrand48 (void)

long int 

Generates pseudo-random numbers evenly distributed between [0, 2^31).

nrand48 (unsigned short xsubi[3])

long int 

Generates pseudo-random numbers evenly distributed between [0, 2^31).

mrand48 (void)

long 

Generates pseudo-random numbers evenly distributed between [-2^31, 2^31).

jrand48 (unsigned short xsubi[3])

long 

Generates pseudo-random numbers evenly distributed between [-2^31, 2^31).

srand48 (long int seedval)

void 

Sets the start seed value for the pseudo-random number generator.

seed48 (unsigned short[3])

unsigned short * 

Generates an evenly distributed pseudo-random seed.

lcong48 (unsigned short param[7])

void 

Sets the seed and related algorithm parameters for the pseudo-random number generator.

mktemp (char *template)

char * 

Creates a unique temporary file name.

mkstemps (char *template, int suffixlen)

int 

Creates and opens a unique temporary file.

mkostemps (char *template, int suffixlen, int flags)

int 

Creates and opens a unique temporary file.

valloc (size_t size)

void * 

Allocates memory with the specified size and aligns the allocated memory by page size.

ecvt (double number, int ndigits, int *decpt, int *sign)

char * 

Converts a double-precision floating-point number into a string.

fcvt (double number, int ndigits, int *decpt, int *sign)

char * 

Converts a floating-point number to a string.

gcvt (double x, int n, char *b)

char * 

Converts a floating-point number to a string.