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   │
       ├───────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │clock_getcpuclockid()                                          │ 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)