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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 4.15 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                             2017-09-15            CLOCK_GETCPUCLOCKID(3)