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pthread_getcpuclockid

Section: C Library Functions (3)
Updated: 202-0-20
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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 CP-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: Pe-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	M-Safe

STANDARDS

POSIX.-2008.

HISTORY

glibc 2.2. POSIX.-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 pe-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 <err.h> #include <errno.h> #include <pthread.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/time.h> #include <time.h> #include <unistd.h> static void * thread_start(void *arg) {
    printf("Subthread starting infinite loop[rs]n");
    for (;;)
        continue; } static void pclock(char *msg, clockid_t cid) {
    struct timespec ts;
    printf("%s", msg);
    if (clock_gettime(cid, &ts) == -1)
        err(EXIT_FAILURE, "clock_gettime");
    printf("%4jd.%03ld[rs]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)
        errc(EXIT_FAILURE, s, "pthread_create");
    printf("Main thread sleeping[rs]n");
    sleep(1);
    printf("Main thread consuming some CPU time...[rs]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)
        errc(EXIT_FAILURE, 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)
        errc(EXIT_FAILURE, s, "pthread_getcpuclockid");
    pclock("Subthread CPU time: 1    ", cid);
    exit(EXIT_SUCCESS);         /* Terminates both threads */ }

Index

Program source

SEE ALSO