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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).

       ┌──────────────────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├──────────────────────┼───────────────┼─────────┤
       │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

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       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at https://www.kernel.org/doc/man-pages/.