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