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 4.10 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				  2016-03-15		CLOCK_GETCPUCLOCKID(3)