clock_getcpuclockid(3)

NAME
clock_getcpuclockid - obtain ID of a process CPU-time clock

LIBRARY
Standard C library (libc, -lc), since glibc 2.17

Before glibc 2.17, Real-time library (librt, -lrt)

SYNOPSIS
#include <time.h>

int clock_getcpuclockid(pid_t pid, clockid_t *clockid);

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

clock_getcpuclockid():
    _POSIX_C_SOURCE >= 200112L

DESCRIPTION
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 clockid. 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.

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 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.

ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value
 | Thread safety | MT-Safe

STANDARDS
POSIX.1-2008.

HISTORY
glibc 2.2. POSIX.1-2001.

NOTES
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.

EXAMPLES
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 <stdint.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <time.h>
    #include <unistd.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 %jd.%09ld seconds\n",
               argv[1], (intmax_t) ts.tv_sec, ts.tv_nsec);
        exit(EXIT_SUCCESS);
    }

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