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timespec_get

Section: C Library Functions (3)
Updated: 202-0-11
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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);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)): 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 no-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 syste-wide time base that measures real (i.e., wal-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 proces-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 threa-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).

Interface	Attribute	Value
timespec_get(), timespec_getres()	Thread safety	M-Safe

STANDARDS

timespec_get(): C23, POSIX.-2024. TIME_UTC C23 (though ISO C doesn't specify the time epoch), POSIX.-2024.
timespec_getres(): TIME_MONOTONIC TIME_ACTIVE TIME_THREAD_ACTIVE C23.

HISTORY

timespec_get(): TIME_UTC C11, POSIX.-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.