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.

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
       This  page  is  part of release 3.25 of the Linux man-pages project.  A description of the project, and information about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                                                      2009-02-08                                   PTHREAD_GETCPUCLOCKID(3)