mirror of https://github.com/mkerrisk/man-pages
166 lines
4.3 KiB
Groff
166 lines
4.3 KiB
Groff
.\" Copyright (c) 2008, Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH CLOCK_GETCPUCLOCKID 3 2015-03-02 "Linux" "Linux Programmer's Manual"
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.SH NAME
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clock_getcpuclockid \- obtain ID of a process CPU-time clock
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.SH SYNOPSIS
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.B #include <time.h>
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.nf
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.sp
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.BI "int clock_getcpuclockid(pid_t " pid ", clockid_t *" clock_id );
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.fi
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.sp
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Link with \fI\-lrt\fP (only for glibc versions before 2.17).
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.sp
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.ad l
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR clock_getcpuclockid ():
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.RS 4
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_XOPEN_SOURCE\ >=\ 600 || _POSIX_C_SOURCE\ >=\ 200112L
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.RE
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.ad
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.SH DESCRIPTION
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The
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.BR clock_getcpuclockid ()
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function obtains the ID of the CPU-time clock of the process whose ID is
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.IR pid ,
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and returns it in the location pointed to by
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.IR clock_id .
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If
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.I pid
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is zero, then the clock ID of the CPU-time clock
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of the calling process is returned.
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.SH RETURN VALUE
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On success,
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.BR clock_getcpuclockid ()
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returns 0;
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on error, it returns one of the positive error numbers listed in ERRORS.
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.SH ERRORS
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.TP
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.B ENOSYS
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The kernel does not support obtaining the per-process
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CPU-time clock of another process, and
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.I pid
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does not specify the calling process.
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.TP
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.B EPERM
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The caller does not have permission to access
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the CPU-time clock of the process specified by
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.IR pid .
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(Specified as an optional error in POSIX.1-2001;
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does not occur on Linux unless the kernel does not support
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obtaining the per-process CPU-time clock of another process.)
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.TP
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.B ESRCH
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There is no process with the ID
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.IR pid .
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.SH VERSIONS
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The
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.BR clock_getcpuclockid ()
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function is available in glibc since version 2.2.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lbw21 lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR clock_getcpuclockid ()
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T} Thread safety MT-Safe
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.TE
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.SH CONFORMING TO
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POSIX.1-2001.
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.SH NOTES
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Calling
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.BR clock_gettime (2)
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with the clock ID obtained by a call to
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.BR clock_getcpuclockid ()
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with a
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.I pid
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of 0,
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is the same as using the clock ID
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.BR CLOCK_PROCESS_CPUTIME_ID .
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.SH EXAMPLE
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The example program below obtains the
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CPU-time clock ID of the process whose ID is given on the command line,
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and then uses
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.BR clock_gettime (2)
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to obtain the time on that clock.
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An example run is the following:
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.in +4n
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.nf
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.RB "$" " ./a.out 1" " # Show CPU clock of init process"
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CPU-time clock for PID 1 is 2.213466748 seconds
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.fi
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.in
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.SS Program source
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\&
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.nf
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#define _XOPEN_SOURCE 600
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#include <stdio.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <time.h>
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int
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main(int argc, char *argv[])
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{
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clockid_t clockid;
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struct timespec ts;
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if (argc != 2) {
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fprintf(stderr, "%s <process\-ID>\\n", argv[0]);
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exit(EXIT_FAILURE);
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}
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if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {
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perror("clock_getcpuclockid");
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exit(EXIT_FAILURE);
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}
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if (clock_gettime(clockid, &ts) == \-1) {
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perror("clock_gettime");
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exit(EXIT_FAILURE);
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}
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printf("CPU-time clock for PID %s is %ld.%09ld seconds\\n",
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argv[1], (long) ts.tv_sec, (long) ts.tv_nsec);
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exit(EXIT_SUCCESS);
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}
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.fi
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.SH SEE ALSO
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.BR clock_getres (2),
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.BR timer_create (2),
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.BR pthread_getcpuclockid (3),
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.BR time (7)
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