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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.

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_get-
     time(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 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 */ }