clock_getcpuclockid

Langue: en

Version: 2009-02-20 (MeeGo - 06/11/10)

Section: 3 (Bibliothèques de fonctions)

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);
 

Link with -lrt.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

clock_getcpuclockid(): _XOPEN_SOURCE >= 600

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 a positive error number.

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 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.

VERSIONS

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

CONFORMING TO

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.

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);
 }
 

SEE ALSO

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

COLOPHON

This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.