clock_getcpuclockid (3)
Leading comments
Copyright (c) 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpages@gmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission ...
NAME
clock_getcpuclockid - obtain ID of a process CPU-time clockSYNOPSIS
#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():
- _XOPEN_SOURCE >= 600 || _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 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 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.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); }