clock_gettime, clock_settime - Obtains or sets the time
for the specified clock (P1003.1b)
int clock_gettime ( clockid_t clock_id, struct timespec
int clock_settime ( clockid_t clock_id, const struct timespec
Realtime Library (librt.so, librt.a)
The clock type used to obtain the time for the clock that
is set. The CLOCK_REALTIME clock is supported and represents
the TIME-OF-DAY clock for the system. A pointer to
a timespec data structure.
The clock_gettime function returns the current time (in
seconds and nanoseconds) for the specified clock. The
clock_settime function sets the specified clock. The
CLOCK_REALTIME clock measures the amount of time elapsed
since 00:00:00:00 January 1, 1970 Greenwich Mean Time
(GMT), otherwise known as the Epoch. Time values that
fall between two non-negative integer multiples of the
resolution are truncated down to the smaller multiple of
You must have superuser privileges to use the clock_settime
On a successful call to the clock_gettime or clock_settime
functions, a value of 0 (zero) is returned.
On an unsuccessful call, a value of -1 is returned and
errno is set to indicate that an error occurred.
The clock_gettime and clock_settime functions fail under
the following conditions: The clock_id argument does not
specify a known clock. The value pointed to by the tp
argument to the clock_settime function is outside the
range for the given clock_id. The tp argument specified a
nanosecond value less than zero or greater than or equal
to 1000 million. The requesting process does not have the
appropriate privilege to set the specified clock.
Functions: time(1), clock_getres(3), ctime(3), timer_gettime(3)
Guide to Realtime Programming
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