[Go to CFHT Home Page] Man Pages
Back to Software Index  BORDER=0Manpage Top Level
    clock_settime(3R) manual page Table of Contents

Name

clock_settime, clock_gettime, clock_getres - high-resolution clock operations

Synopsis

cc [ flag ... ] file ... -lposix4 [ library ... ]

#include <time.h>

int clock_settime(clockid_t clock_id, const struct timespec *tp);

int clock_gettime(clockid_t clock_id, struct timespec *tp);

int clock_getres(clockid_t clock_id, struct timespec *res);

struct timespec {
   time_t    tv_sec;    /* seconds */

   long    tv_nsec;    /* and nanoseconds */

};

MT-Level

clock_gettime() is Async-Signal-Safe

Description

clock_settime() sets the specified clock, clock_id, to the value specified by tp. The calling process must have an effective user ID of 0.

clock_gettime() returns the current value tp for the specified clock, clock_id.

The resolution of any clock can be obtained by calling clock_getres(). If res is not NULL, the resolution of the specified clock is stored in res.

The clock_id for the real-time clock for the system is CLOCK_REALTIME. The values returned by clock_gettime() and specified by clock_settime() represent the amount of time (in seconds and nanoseconds) since 00:00 Universal Coordinated Time, January 1, 1970.

Return Values

clock_settime(), clock_gettime(), and clock_getres() return 0 upon success, otherwise they return -1 and set errno to indicate the error condition.

Errors

EINVAL
clock_id does not specify a known clock.

The tp argument to clock_settime() is outside the range for the given clock id.

The tp argument to clock_settime() specified a nanosecond value less than zero or greater than or equal to 1,000,000,000.

ENOSYS
clock_settime(), clock_gettime(), or clock_getres() is not supported by this implementation.
EPERM
The requesting process does not have the appropriate privilege to set the specified clock.

See Also

time(2) , ctime(3C) , timer_gettime(3R)

Notes

Clock resolutions are implementation defined and are not settable by a process. Time values that are between two consecutive non-negative integer multiples of the resolution of the specified clock are truncated down to the smaller multiple of the resolution.

Table of Contents