Name
clock_getcpuclockid - obtain ID of a process CPU-time clockLibrary
Standard C library ( libc ", " -lc ), since glibc 2.17Before 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 ispid
, 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).Interface | Attribute | Value |
T} | Thread safety | MT-Safe |
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>\en", 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\en", 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)