www.LinuxHowtos.org

clock_getcpuclockid

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

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); }

Index

Program source

SEE ALSO