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clock_getcpuclockid(3) Library Functions Manual clock_getcpuclockid(3)
NAME
clock_getcpuclockid - obtain ID of a process CPU-time clock
LIBRARY
Standard C library (libc, -lc), since glibc 2.17
Before glibc 2.17, Real-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 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.
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 ob-
taining the per-process CPU-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 at-
tributes(7).
+--------------------------------------------+---------------+---------+
|Interface | Attribute | Value |
+--------------------------------------------+---------------+---------+
|clock_getcpuclockid() | Thread safety | MT-Safe |
+--------------------------------------------+---------------+---------+
STANDARDS
POSIX.1-2008.
HISTORY
glibc 2.2. POSIX.1-2001.
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 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);
}
SEE ALSO
clock_getres(2), timer_create(2), pthread_getcpuclockid(3), time(7)
Linux man-pages 6.04 2023-03-30 clock_getcpuclockid(3)
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