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

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ pthread_getcpuclockid()                                                     │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       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.

ENOENT Per-thread CPU time clocks are not supported by the system.

       ESRCH  No thread with the ID thread could be found.

       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

   Programsource

       /* 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 */
       }

       glibc 2.2.  POSIX.1-2001.

       POSIX threads library (libpthread, -lpthread)

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

       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.

       On success, this function returns 0; on error, it returns a nonzero error number.

clock_gettime(2),    clock_settime(2),    timer_create(2),    clock_getcpuclockid(3),    pthread_self(3),
       pthreads(7), time(7)

Linux man-pages 6.9.1                              2024-06-15                           pthread_getcpuclockid(3)

       POSIX.1-2008.

#include<pthread.h>#include<time.h>intpthread_getcpuclockid(pthread_tthread,clockid_t*clockid);