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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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clock_getcpuclockid(3) Library Functions Manual clock_getcpuclockid(3)
clock_getcpuclockid - obtain ID of a process CPU-time clock
Standard C library (libc, -lc), since glibc 2.17
Before glibc 2.17, Real-time library (librt, -lrt)
#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
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 clockid. If pid is zero, then the clock ID
of the CPU-time clock of the calling process is returned.
On success, clock_getcpuclockid() returns 0; on error, it returns
one of the positive error numbers listed in 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.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ clock_getcpuclockid() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008.
glibc 2.2. POSIX.1-2001.
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.
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 <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>\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\n",
argv[1], (intmax_t) ts.tv_sec, ts.tv_nsec);
exit(EXIT_SUCCESS);
}
clock_getres(2), timer_create(2), pthread_getcpuclockid(3),
time(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.10.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-02-02. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.10 2024-07-23 clock_getcpuclockid(3)
Pages that refer to this page: clock_getres(2), clock_nanosleep(2), timer_create(2), clockid_t(3type), pthread_getcpuclockid(3), time(7)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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