NAME¶

timespec_get, timespec_getres - ISO C interface to clock and time functions

LIBRARY¶

Standard C library (libc, -lc)

SYNOPSIS¶

#include <time.h>

int timespec_get(struct timespec *res, int base);
int timespec_getres(struct timespec *tp, int base);

timespec_get(), TIME_UTC:

    _ISOC11_SOURCE

timespec_getres(), TIME_MONOTONIC, TIME_ACTIVE, TIME_THREAD_ACTIVE:

    _ISOC23_SOURCE

DESCRIPTION¶

The timespec_get() function stores the current time, based on the specified time base, in the timespec(3type) structure pointed to by res.

The timespec_getres() function stores the resolution of times retrieved by timespec_get() with the specified time base in the timespec(3type) structure pointed to by tp, if tp is non-NULL. For a particular time base, the resolution is constant for the lifetime of the calling process.

The time base base is one of the following:

TIME_UTC

A system-wide time base that measures real (i.e., wall-clock) time. The time and resolution in this time base are the same as those retrieved by clock_gettime(CLOCK_REALTIME, res) and clock_getres(CLOCK_REALTIME, tp), respectively.

TIME_MONOTONIC

A time base that measures time since an unspecified point in the past, where the time within a process will not decrease even if the system's real time clock is set or adjusted. The time and resolution in this time base are the same as those retrieved by clock_gettime(CLOCK_MONOTONIC, res) and clock_getres(CLOCK_MONOTONIC, tp), respectively.

TIME_ACTIVE

A process-specific time base that measures CPU time consumed by the calling process. The time and resolution in this time base are the same as those retrieved by clock_gettime(CLOCK_PROCESS_CPUTIME_ID, res) and clock_getres(CLOCK_PROCESS_CPUTIME_ID, tp), respectively.

TIME_THREAD_ACTIVE

A thread-specific time base that measures CPU time consumed by the calling thread. The time and resolution in this time base are the same as those retrieved by clock_gettime(CLOCK_THREAD_CPUTIME_ID, res) and clock_getres(CLOCK_THREAD_CPUTIME_ID, tp), respectively.

RETURN VALUE¶

timespec_get() returns the nonzero base if it is a supported time base and the current time was successfully retrieved, or 0 otherwise.

timespec_getres() returns the nonzero base if it is a supported time base, or 0 otherwise.

ATTRIBUTES¶

For an explanation of the terms used in this section, see attributes(7).

STANDARDS¶

timespec_get()

C23, POSIX.1-2024.

TIME_UTC

C23 (though ISO C doesn't specify the time epoch), POSIX.1-2024.

timespec_getres()

TIME_MONOTONIC

TIME_ACTIVE

TIME_THREAD_ACTIVE

C23.

HISTORY¶

timespec_get()

TIME_UTC

C11, POSIX.1-2024, glibc 2.16, musl 1.1.10.

timespec_getres()

C23, glibc 2.34.

TIME_MONOTONIC

TIME_ACTIVE

TIME_THREAD_ACTIVE

C23, glibc 2.43.

SEE ALSO¶

clock_gettime(2), clock_getres(2)