NAME

clock_getcpuclockid - obtain ID of a process CPU-time clock

SYNOPSIS

#include <time.h>

int clock_getcpuclockid(pid_t pid, clockid_t *clock_id);

Link with -lrt.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

clock_getcpuclockid(): _XOPEN_SOURCE >= 600

DESCRIPTION

The clock_getcpuclockid() obtains the ID of the CPU-time clock of the process whose ID is pid, and returns it in the location pointed to by clock_id. If pid is zero, then the clock ID of the CPU-time clock of the calling process is returned.

RETURN VALUE

On success, clock_getcpuclockid() returns 0; on error, it returns a positive error number.

ERRORS

ENOSYS

The kernel does not support obtaining the per-process CPU-time clock of another process, and pid does not specify the calling process.

EPERM

The caller does not have permission to access the CPU-time clock of the process specified by pid. (Specified as an optional error in POSIX.1-2001; does not occur on Linux unless the kernel does not support obtaining the per-process CPU-time clock of another process.)

ESRCH

There is no process with the ID pid.

VERSIONS

The clock_getcpuclockid() function is available in glibc since version 2.2.

CONFORMING TO

POSIX.1-2001.

NOTES

Calling clock_gettime(3) with the clock ID obtained by a call to clock_getcpuclockid() with a pid of 0, is the same as using the clock ID CLOCK_PROCESS_CPUTIME_ID.

EXAMPLE

The example program below obtains the CPU-time clock ID of the process whose ID is given on the command line, and then uses clock_gettime(3) to obtain the time on that clock. An example run is the following:

$ ./a.out 1                 # Show CPU clock of init process
CPU-time clock for PID 1 is 2.213466748 seconds

#define _XOPEN_SOURCE 600
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>
int
main(int argc, char *argv[])
{

    clockid_t clockid;

    struct timespec ts;

    if (argc != 2) {

        fprintf(stderr, "%s <process-ID>\n", argv[0]);
	exit(EXIT_FAILURE);

    }

    if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {
	perror("clock_getcpuclockid");
	exit(EXIT_FAILURE);

    }

    if (clock_gettime(clockid, &ts) == -1) {
	perror("clock_gettime");
	exit(EXIT_FAILURE);

    }

    printf("CPU-time clock for PID %s is %ld.%09ld seconds\n",
	    argv[1], (long) ts.tv_sec, (long) ts.tv_nsec);

    exit(EXIT_SUCCESS);
}

SEE ALSO

clock_getres(3), time(7)

COLOPHON

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