# time.h ## **Overview** **Related Modules:** [TIME](TIME.md) **Description:** Provides time-related structures and functions. You can perform time-related management operations, including obtaining and setting broken-down time and system ticks, and manipulating timers. **Since:** 1.0 **Version:** 1.0 ## **Summary** ## Data Structures

Data Structure Name

Description

tm

Describes date and time information.

itimerspec

Sets a timer.

## Macros

Macro Name and Value

Description

CLOCK_REALTIME   0

Defines the clock that runs in real time.

## Functions

Function Name

Description

time (time_t *t)

time_t 

Obtains the time.

difftime (time_t time1, time_t time2)

double 

Calculates the difference between two times, in seconds.

mktime (struct tm *tm)

time_t 

Converts the broken-down time in the tm structure into seconds.

strftime (char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)

size_t 

Converts the broken-down time in the tm structure to a string in the required format.

gmtime (const time_t *t)

struct tm * 

Converts the number of seconds to the UTC time in the tm structure.

localtime (const time_t *t)

struct tm * 

Converts the number of seconds to the local time in the tm structure.

asctime (const struct tm *tm)

char * 

Converts the broken-down time in the tm structure into a string.

ctime (const time_t *timep)

char * 

Converts the date and time into a string.

strftime_l (char *__restrict s, size_t n, const char *__restrict f, const struct tm *__restrict tm, locale_t loc)

size_t 

Converts the broken-down time in the tm structure to a string in a specified programming language and format.

gmtime_r (const time_t *__restrict t, struct tm *__restrict tm)

struct tm * 

Converts the number of seconds to the UTC time in the tm structure. (This function is reentrant.)

localtime_r (const time_t *__restrict t, struct tm *__restrict tm)

struct tm * 

Converts the number of seconds to the local time in the tm structure. (This function is reentrant.)

asctime_r (const struct tm *__restrict tm, char *__restrict buf)

char * 

Converts the broken-down time in the tm structure into a string. (This function is reentrant.)

ctime_r (const time_t *t, char *buf)

char * 

Converts the date and time into a string. (This function is reentrant.)

nanosleep (const struct timespec *tspec1, struct timespec *tspec2)

int 

Pauses the current thread until a specified time arrives.

clock_getres (clockid_t id, struct timespec *tspec)

int 

Obtains the precision of a clock.

clock_gettime (clockid_t id, struct timespec *tspec)

int 

Obtains the time of a clock.

clock_settime (clockid_t id, const struct timespec *tspec)

int 

Sets the time for a clock.

clock_nanosleep (clockid_t id, int flag, const struct timespec *tspec1, struct timespec *tspec2)

int 

Pauses the current thread until a specified time of a clock arrives.

timer_create (clockid_t id, struct sigevent *__restrict evp, timer_t *__restrict t)

int 

Creates a timer for the process.

timer_delete (timer_t t)

int 

Deletes a timer for the process.

timer_settime (timer_t t, int flags, const struct itimerspec *__restrict val, struct itimerspec *__restrict old)

int 

Sets a timer for the process.

timer_gettime (timer_t t, struct itimerspec *tspec)

int 

Obtains a timer of the process.

timer_getoverrun (timer_t t)

int 

Obtains the number of times that a timer overruns.

strptime (const char *s, const char *format, struct tm *tm)

char * 

Converts a time string to the broken-down time in the tm structure.

getdate (const char *buf)

struct tm * 

Converts a time string to the broken-down time in the tm structure.

stime (const time_t *t)

int 

Sets the system time.

timegm (struct tm *tm)

time_t 

Converts the broken-down time in the tm structure to the number of seconds.