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
 | 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)