clock_getcpuclockid

Section: C Library Functions (3)
Updated: 202-0-17
Index Return to Main Contents

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NAME

clock_getcpuclockid - obtain ID of a process CP-time clock  

LIBRARY

Standard C library (libc,~-lc), since glibc 2.17 Before glibc 2.17, Rea-time library (librt,~-lrt)  

SYNOPSIS

#include <time.h>

int clock_getcpuclockid(pid_t pid, clockid_t *clockid);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)): clock_getcpuclockid():

    _POSIX_C_SOURCE >= 200112L

 

DESCRIPTION

The clock_getcpuclockid() function obtains the ID of the CP-time clock of the process whose ID is pid, and returns it in the location pointed to by clockid. If pid is zero, then the clock ID of the CP-time clock of the calling process is returned.  

RETURN VALUE

On success, clock_getcpuclockid() returns 0; on error, it returns one of the positive error numbers listed in ERRORS.  

ERRORS

ENOSYS

The kernel does not support obtaining the pe-process CP-time clock of another process, and pid does not specify the calling process.

EPERM

The caller does not have permission to access the CP-time clock of the process specified by pid. (Specified in POSIX.-2001; does not occur on Linux unless the kernel does not support obtaining the pe-process CP-time clock of another process.)

ESRCH

There is no process with the ID pid.

 

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
clock_getcpuclockid()	Thread safety	M-Safe

 

STANDARDS

POSIX.-2008.  

HISTORY

glibc 2.2. POSIX.-2001.  

NOTES

Calling clock_gettime(2) with the clock ID obtained by a call to clock_getcpuclockid() with a pid of 0, is the same as using the clock ID CLOCK_PROCESS_CPUTIME_ID.  

EXAMPLES

The example program below obtains the CP-time clock ID of the process whose ID is given on the command line, and then uses clock_gettime(2) to obtain the time on that clock. An example run is the following: $ ./a.out 1 # Show CPU clock of init process CPU-time clock for PID 1 is 2.213466748 seconds  

Program source

#define _XOPEN_SOURCE 600 #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <time.h> #include <unistd.h> int main(int argc, char *argv[]) {
    clockid_t clockid;
    struct timespec ts;
    if (argc != 2) {
        fprintf(stderr, "%s <process-ID>[rs]n", argv[0]);
        exit(EXIT_FAILURE);
    }
    if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {
        perror("clock_getcpuclockid");
        exit(EXIT_FAILURE);
    }
    if (clock_gettime(clockid, &ts) == -1) {
        perror("clock_gettime");
        exit(EXIT_FAILURE);
    }
    printf("CPU-time clock for PID %s is %jd.%09ld seconds[rs]n",
           argv[1], (intmax_t) ts.tv_sec, ts.tv_nsec);
    exit(EXIT_SUCCESS); }  

SEE ALSO

clock_getres(2), timer_create(2), pthread_getcpuclockid(3), time(7)

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Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

STANDARDS

HISTORY

NOTES

EXAMPLES

Program source

SEE ALSO