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clock_getcpuclockid(3)

Linux
2019-03-06

manpages-dev

Manual pages about using GNU/Linux for development

man-pages

Linux kernel and C library user-space interface documentation

NAME

clock_getcpuclockid - obtain ID of a process CPU-time clock

SYNOPSIS

#include <time.h>

int clock_getcpuclockid(pid_t pid, clockid_t *clock_id);
Link with -lrt (only for glibc versions before 2.17).
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 CPU-time clock of the process whose ID is pid, and returns it in the location pointed to by clock_id. If pid is zero, then the clock ID of the CPU-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 per-process CPU-time clock of another process, and pid does not specify the calling process.
EPERM The caller does not have permission to access the CPU-time clock of the process specified by pid. (Specified in POSIX.1-2001; does not occur on Linux unless the kernel does not support obtaining the per-process CPU-time clock of another process.)
ESRCH There is no process with the ID pid.

VERSIONS

The clock_getcpuclockid() function is available in glibc since version 2.2.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
Thread safety MT-Safe

CONFORMING TO

POSIX.1-2001, POSIX.1-2008.

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.

EXAMPLE

The example program below obtains the CPU-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 <stdio.h> #include <unistd.h> #include <stdlib.h> #include <time.h>
int main(int argc, char *argv[]) {
clockid_t clockid;
struct timespec ts;
if (argc != 2) {
fprintf(stderr, "%s <process-ID>\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 %ld.%09ld seconds\n",
argv[1], (long) ts.tv_sec, (long) ts.tv_nsec);
exit(EXIT_SUCCESS); }

COLOPHON

This page is part of release 5.00 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
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