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);
}