clock_gettime(3)clock_gettime(3)NAME
clock_gettime, clock_settime - Obtains or sets the time for the speci‐
fied clock (P1003.1b)
SYNOPSIS
#include <time.h>
int clock_gettime ( clockid_t clock_id, struct timespec *tp);
int clock_settime ( clockid_t clock_id, const struct timespec *tp);
LIBRARY
Realtime Library (librt.so, librt.a)
PARAMETERS
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.
DESCRIPTION
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 the resolution.
You must have superuser privileges to use the clock_settime function.
RETURN VALUES
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.
ERRORS
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 mil‐
lion. The requesting process does not have the appropriate privilege
to set the specified clock.
SEE ALSO
Functions: time(1), clock_getres(3), ctime(3), timer_gettime(3)
Guide to Realtime Programming
clock_gettime(3)