clock_getcpuclockid - obtain ID of a process CPU-time clock
#include <time.h>
int clock_getcpuclockid(pid_t pid, clockid_t *clock_id);
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
clock_id. 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
#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);
}
clock_getres(2),
timer_create(2),
pthread_getcpuclockid(3),
time(7)