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 */ }  

SEE ALSO

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

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Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

STANDARDS

HISTORY

NOTES

EXAMPLES

Program source

SEE ALSO