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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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CLOCK_GETCPUCLOCKID(3) Linux Programmer's Manual CLOCK_GETCPUCLOCKID(3)
clock_getcpuclockid - obtain ID of a process CPU-time clock
#include <time.h>
int clock_getcpuclockid(pid_t pid, clockid_t *clockid);
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
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.
The clock_getcpuclockid() function is available in glibc since
version 2.2.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│clock_getcpuclockid() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2001, POSIX.1-2008.
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 <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 %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 release 5.12 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/.
Linux 2021-03-22 CLOCK_GETCPUCLOCKID(3)
Pages that refer to this page: clock_getres(2), clock_nanosleep(2), timer_create(2), pthread_getcpuclockid(3), system_data_types(7), time(7)
Copyright and license for this manual page
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