pthread_getcpuclockid(3)   Library Functions Manual   pthread_getcpuclockid(3)

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

LIBRARY
       POSIX threads library (libpthread, -lpthread)

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

       int pthread_getcpuclockid(pthread_t thread, clockid_t *clockid);

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
       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.

ATTRIBUTES
       For an explanation of the terms used in this section, see
       attributes(7).

       +--------------------------------------------+---------------+---------+
       |Interface                                   | Attribute     | Value   |
       +--------------------------------------------+---------------+---------+
       |pthread_getcpuclockid ()                    | Thread safety | MT-Safe |
       +--------------------------------------------+---------------+---------+
STANDARDS
       POSIX.1-2008.

HISTORY
       glibc 2.2.  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.

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
       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 <errno.h>
       #include <pthread.h>
       #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #include <time.h>
       #include <unistd.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("%4jd.%03ld\n", (intmax_t) ts.tv_sec, ts.tv_nsec / 1000000);
       }

       int
       main(void)
       {
           pthread_t thread;
           clockid_t cid;
           int 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 (unsigned int 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)

Linux man-pages 6.7               2023-10-31          pthread_getcpuclockid(3)