Man page - clock_getcpuclockid(3)

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Manual

clock_getcpuclockid

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
STANDARDS
HISTORY
NOTES
EXAMPLES
Program source
SEE ALSO

NAME

clock_getcpuclockid - obtain ID of a process CPU-time clock

LIBRARY

Standard C library ( libc , -lc ), since glibc 2.17

Before glibc 2.17, Real-time library ( librt , -lrt )

SYNOPSIS

#include <time.h>

int clock_getcpuclockid(pid_t pid , clockid_t * clockid );

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 .

ATTRIBUTES

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

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STANDARDS

POSIX.1-2008.

HISTORY

glibc 2.2. 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 .

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 <stdlib.h>
#include <time.h>
#include <unistd.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);
}