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



NAME
       pthread_getcpuclockid - retrieve ID of a thread's CPU time clock

SYNOPSIS
       #include <pthread.h>
       #include <time.h>

       int pthread_getcpuclockid(pthread_t thread, clockid_t *clock_id);

       Compile and link with -pthread.

DESCRIPTION
       The  pthread_getcpuclockid()  function returns the clock ID for the CPU
       time clock of the thread thread.

RETURN VALUE
       On success, this function returns 0; on error,  it  returns  a  nonzero
       error number.

ERRORS
       ENOENT Per-thread CPU time clocks are not supported by the system.

       ESRCH  No thread with the ID thread could be found.

VERSIONS
       This 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	  |
       +------------------------+---------------+---------+
       |pthread_getcpuclockid() | Thread safety | MT-Safe |
       +------------------------+---------------+---------+
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008.

NOTES
       When thread refers to the calling  thread,  this	 function  returns  an
       identifier  that	 refers	 to  the  same clock manipulated by clock_get-
       time(2)	 and   clock_settime(2)	   when	   given    the	   clock    ID
       CLOCK_THREAD_CPUTIME_ID.

EXAMPLE
       The  program  below  creates a thread and then uses clock_gettime(2) to
       retrieve the total process CPU time, and the per-thread CPU  time  con-
       sumed by the two threads.  The following shell session shows an example
       run:

	   $ ./a.out
	   Main thread sleeping
	   Subthread starting infinite loop
	   Main thread consuming some CPU time...
	   Process total CPU time:    1.368
	   Main thread CPU time:      0.376
	   Subthread CPU time:	      0.992

   Program source

       /* Link with "-lrt" */

       #include <time.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>
       #include <pthread.h>
       #include <string.h>
       #include <errno.h>

       #define handle_error(msg) \
	       do { perror(msg); exit(EXIT_FAILURE); } while (0)

       #define handle_error_en(en, msg) \
	       do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

       static void *
       thread_start(void *arg)
       {
	   printf("Subthread starting infinite loop\n");
	   for (;;)
	       continue;
       }

       static void
       pclock(char *msg, clockid_t cid)
       {
	   struct timespec ts;

	   printf("%s", msg);
	   if (clock_gettime(cid, &ts) == -1)
	       handle_error("clock_gettime");
	   printf("%4ld.%03ld\n", ts.tv_sec, ts.tv_nsec / 1000000);
       }

       int
       main(int argc, char *argv[])
       {
	   pthread_t thread;
	   clockid_t cid;
	   int j, s;

	   s = pthread_create(&thread, NULL, thread_start, NULL);
	   if (s != 0)
	       handle_error_en(s, "pthread_create");

	   printf("Main thread sleeping\n");
	   sleep(1);

	   printf("Main thread consuming some CPU time...\n");
	   for (j = 0; j < 2000000; j++)
	       getppid();

	   pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);

	   s = pthread_getcpuclockid(pthread_self(), &cid);
	   if (s != 0)
	       handle_error_en(s, "pthread_getcpuclockid");
	   pclock("Main thread CPU time:   ", cid);

	   /* The preceding 4 lines of code could have been replaced by:
	      pclock("Main thread CPU time:   ", CLOCK_THREAD_CPUTIME_ID); */

	   s = pthread_getcpuclockid(thread, &cid);
	   if (s != 0)
	       handle_error_en(s, "pthread_getcpuclockid");
	   pclock("Subthread CPU time: 1    ", cid);

	   exit(EXIT_SUCCESS);	       /* Terminates both threads */
       }

SEE ALSO
       clock_gettime(2),  clock_settime(2),   timer_create(2),	 clock_getcpu-
       clockid(3), pthread_self(3), pthreads(7), 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				  2015-08-08	      PTHREAD_GETCPUCLOCKID(3)