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); |
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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
piddoes 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 as an optional error 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.
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 3.52 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man−pages/.
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Copyright (c) 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END |