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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.

CONFORMING TO

       POSIX.1-2001.

NOTES

       When  thread  refers  to  the  calling thread, this function returns an
       identifier   that   refers   to   the   same   clock   manipulated   by
       clock_gettime(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
       consumed 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_getcpuclockid(3), pthread_self(3), pthreads(7), time(7)

COLOPHON

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       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.