PTHREAD_GETCPUCLOCKID(3)

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 *clockid);

       Compile and link with -pthread.

DESCRIPTION
       The  pthread_getcpuclockid()  function  obtains  the ID of the CPU-time
       clock of the thread whose ID is given in thread, and returns it in  the
       location pointed to by clockid.

RETURN VALUE
       On success, this function returns 0; on error, it returns a nonzero er-
       ror 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  at-
       tributes(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.

EXAMPLES
       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 5.07 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                             2020-06-09          PTHREAD_GETCPUCLOCKID(3)