clocks.2 (2010 09)

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clocks(2) clocks(2)

ERRORS

If any of the following conditions occur, the

clock_settime(), clock_gettime()

, and

clock_getres()

functions return −1 and set errno (see errno (2)) to the corresponding value:

[ENOSYS] The functions

clock_settime()

, clock_gettime()

, and clock_getres()

are not supported by this implementation.

[EINVAL] The

clock_id argument does not specify a known clock.

[EINVAL] The

tp argument to clock_settime()

is outside the range for the given

clock_id.

[EINVAL] The

tp argument speciﬁed a nanosecond value less than zero or greater than or equal

to 1000 million.

[EPERM] The requesting process does not have the necessary privileges to set the speciﬁed clock.

[EFAULT] The

tp or res argument points to an invalid address.

EXAMPLES

Advance the system wide realtime clock approximately one hour:

#include <time.h>

#include <errno.h>

struct timespec cur_time, new_time;

if (clock_gettime(CLOCK_REALTIME, &cur_time)) {

perror("clock_gettime(CLOCK_REALTIME) failed");

exit(1);

}

new_time.tv_sec = cur_time.tv_sec + 3600;

new_time.tv_nsec = cur_time.tv_nsec;

if (clock_settime(CLOCK_REALTIME, &new_time)) {

perror("clock_settime(CLOCK_REALTIME) failed");

exit(2);

}

Get the resolution of the user proﬁling clock:

#include <time.h>

#include <errno.h>

struct timespec resolution;

if (clock_getres(CLOCK_PROFILE, &resolution)) {

perror("clock_getres(CLOCK_PROFILE) failed");

exit(1);

}

(void)printf("Resolution of user profiling clock is:\n");

(void)printf("%d seconds and %d nanoseconds.\n",

resolution.tv_sec, resolution.tv_nsec);

AUTHOR

clock_settime(), clock_gettime(), and clock_getres()

were derived from the proposed

IEEE POSIX P1003.4 Standard, Draft 14.