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+'\" t
+.\" Copyright (c) 2008, Linux Foundation, written by Michael Kerrisk
+.\" <mtk.manpages@gmail.com>
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.TH clock_getcpuclockid 3 2023-07-20 "Linux man-pages 6.05.01"
+.SH NAME
+clock_getcpuclockid \- obtain ID of a process CPU-time clock
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc ),
+since glibc 2.17
+.PP
+Before glibc 2.17,
+Real-time library
+.RI ( librt ", " \-lrt )
+.SH SYNOPSIS
+.B #include <time.h>
+.nf
+.PP
+.BI "int clock_getcpuclockid(pid_t " pid ", clockid_t *" clockid );
+.fi
+.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 ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface Attribute Value
+T{
+.na
+.nh
+.BR clock_getcpuclockid ()
+T} Thread safety MT-Safe
+.TE
+.sp 1
+.SH STANDARDS
+POSIX.1-2008.
+.SH HISTORY
+glibc 2.2.
+POSIX.1-2001.
+.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
+\&
+.\" SRC BEGIN (clock_getcpuclockid.c)
+.EX
+#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);
+}
+.EE
+.\" SRC END
+.SH SEE ALSO
+.BR clock_getres (2),
+.BR timer_create (2),
+.BR pthread_getcpuclockid (3),
+.BR time (7)