clock_getcpuclockid

CLOCK_GETCPUCLOCKID(3)     Linux Programmer's Manual    CLOCK_GETCPUCLOCKID(3)



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 (only for glibc versions before 2.17).

   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 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.

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.

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

ATTRIBUTES
       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.

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.

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(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>

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

COLOPHON
       This page is part of release 5.03 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
       https://www.kernel.org/doc/man-pages/.



Linux                             2019-03-06            CLOCK_GETCPUCLOCKID(3)