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| .TH CLOCK_GETCPUCLOCKID 3 2021-03-22 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| clock_getcpuclockid \- obtain ID of a process CPU-time clock |
| .SH SYNOPSIS |
| .B #include <time.h> |
| .nf |
| .PP |
| .BI "int clock_getcpuclockid(pid_t " pid ", clockid_t *" clockid ); |
| .fi |
| .PP |
| Link with \fI\-lrt\fP (only for glibc versions before 2.17). |
| .PP |
| .ad l |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR clock_getcpuclockid (): |
| .nf |
| _POSIX_C_SOURCE >= 200112L |
| .fi |
| .SH DESCRIPTION |
| The |
| .BR clock_getcpuclockid () |
| function obtains the ID of the CPU-time clock of the process whose ID is |
| .IR pid , |
| and returns it in the location pointed to by |
| .IR clockid . |
| If |
| .I pid |
| is zero, then the clock ID of the CPU-time clock |
| of the calling process is returned. |
| .SH RETURN VALUE |
| On success, |
| .BR clock_getcpuclockid () |
| returns 0; |
| on error, it returns one of the positive error numbers listed in ERRORS. |
| .SH ERRORS |
| .TP |
| .B ENOSYS |
| The kernel does not support obtaining the per-process |
| CPU-time clock of another process, and |
| .I pid |
| does not specify the calling process. |
| .TP |
| .B EPERM |
| The caller does not have permission to access |
| the CPU-time clock of the process specified by |
| .IR 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.) |
| .TP |
| .B ESRCH |
| There is no process with the ID |
| .IR pid . |
| .SH VERSIONS |
| The |
| .BR clock_getcpuclockid () |
| function is available in glibc since version 2.2. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR clock_getcpuclockid () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008. |
| .SH NOTES |
| Calling |
| .BR clock_gettime (2) |
| with the clock ID obtained by a call to |
| .BR clock_getcpuclockid () |
| with a |
| .I pid |
| of 0, |
| is the same as using the clock ID |
| .BR CLOCK_PROCESS_CPUTIME_ID . |
| .SH 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 |
| .BR clock_gettime (2) |
| to obtain the time on that clock. |
| An example run is the following: |
| .PP |
| .in +4n |
| .EX |
| .RB "$" " ./a.out 1" " # Show CPU clock of init process" |
| CPU\-time clock for PID 1 is 2.213466748 seconds |
| .EE |
| .in |
| .SS Program source |
| \& |
| .EX |
| #define _XOPEN_SOURCE 600 |
| #include <stdint.h> |
| #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>\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); |
| } |
| .EE |
| .SH SEE ALSO |
| .BR clock_getres (2), |
| .BR timer_create (2), |
| .BR pthread_getcpuclockid (3), |
| .BR time (7) |