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CLOCK_GETCPUCLOCKID(3) | Linux Programmer's Manual | CLOCK_GETCPUCLOCKID(3) |
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 (only for glibc versions before 2.17).
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
clock_getcpuclockid():
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 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.
ATTRIBUTES¶
Multithreading (see pthreads(7))¶
The clock_getcpuclockid() function is thread-safe.
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 3.53 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/.
2013-07-04 | Linux |