clock_getcpuclockid man page

clock_getcpuclockid — obtain ID of a process CPU-time clock


#include <time.h>

int clock_getcpuclockid(pid_t pid, clockid_t *clock_id);

Link with -lrt (only for glibc versions before 2.17).

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


_POSIX_C_SOURCE >= 200112L


The clock_getcpuclockid() function 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 one of the positive error numbers listed in Errors.



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


The caller does not have permission to access the CPU-time clock of the process specified by pid. (Specified 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.)


There is no process with the ID pid.


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


For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
clock_getcpuclockid() Thread safety MT-Safe

Conforming to

POSIX.1-2001, POSIX.1-2008.


Calling clock_gettime(2) 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.


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(2) 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

Program source

#define _XOPEN_SOURCE 600
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>

main(int argc, char *argv[])
    clockid_t clockid;
    struct timespec ts;

    if (argc != 2) {
        fprintf(stderr, "%s <process-ID>\n", argv[0]);

    if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {

    if (clock_gettime(clockid, &ts) == -1) {

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

See Also

clock_getres(2), timer_create(2), pthread_getcpuclockid(3), time(7)


This page is part of release 4.11 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at

Referenced By

clock_getres(2), clock_nanosleep(2), pthread_getcpuclockid(3), time(7), timer_create(2).

2016-03-15 Linux Programmer's Manual