Manpages - clock_getcpuclockid.3

Table of Contents

NAME

clock_getcpuclockid - obtain ID of a process CPU-time clock

SYNOPSIS

#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

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 obtaining the per-process CPU-time clock of another process.)
ESRCH
There is no process with the ID pid.

VERSIONS

The *clock_getcpuclockid*() function is available in glibc since version 2.2.

ATTRIBUTES

For an explanation of the terms used in this section, see *attributes*(7).

Interface Attribute Value
*clock_getcpuclockid*() Thread safety MT-Safe

CONFORMING TO

POSIX.1-2001, POSIX.1-2008.

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 <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);
  }

SEE ALSO

*clock_getres*(2), *timer_create*(2), *pthread_getcpuclockid*(3), *time*(7)

COLOPHON

This page is part of release 5.13 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/.

Author: dt

Created: 2022-02-20 Sun 14:45