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clock_getres.2: Add an example program 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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Michael Kerrisk 2020-04-04 09:32:33 +02:00
parent a48d19162d
commit 16fa57813e
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man2/clock_getres.2
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@ -1,5 +1,6 @@
.\" Copyright (c) 2003 Nick Clifford (zaf@nrc.co.nz), Jan 25, 2003
.\" Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl), Aug 24, 2003
.\" Copyright (c) 2020 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
@ -392,6 +393,90 @@ and
.BR CLOCK_THREAD_CPUTIME_ID ,
on systems that provide such an implementation
(i.e., Linux 2.6.12 and later).
.SH EXAMPLE
The program below demonstrates the use of
.BR clock_gettime ()
and
.BR clock_getres ()
with various clocks.
This is an example of what we might see when running the program:
.PP
.in +4n
.EX
$ \fB./clock_times x\fP
CLOCK_REALTIME : 1585985459.446 (18356 days + 7h 30m 59s)
resolution: 0.000000001
CLOCK_TAI : 1585985496.447 (18356 days + 7h 31m 36s)
resolution: 0.000000001
CLOCK_MONOTONIC : 52395.722 (14h 33m 15s)
resolution: 0.000000001
CLOCK_BOOTTIME : 72691.019 (20h 11m 31s)
resolution: 0.000000001
.EE
.in
.SS Program source
\&
.EX
/* clock_times.c
Licensed under GNU General Public License v2 or later.
*/
#define _XOPEN_SOURCE 600
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#define SECS_IN_DAY (24 * 60 * 60)
static void
displayClock(clockid_t clock, char *name, bool showRes)
{
struct timespec ts;
if (clock_gettime(clock, &ts) == \-1) {
perror("clock_gettime");
exit(EXIT_FAILURE);
}
printf("%\-22s: %10ld.%03ld (", name,
(long) ts.tv_sec, ts.tv_nsec / 1000000);
long days = ts.tv_sec / SECS_IN_DAY;
if (days > 0)
printf("%ld days + ", days);
printf("%2ldh %2ldm %2lds", (ts.tv_sec % SECS_IN_DAY) / 3600,
(ts.tv_sec % 3600) / 60, ts.tv_sec % 60);
printf(")\en");
if (clock_getres(clock, &ts) == \-1) {
perror("clock_getres");
exit(EXIT_FAILURE);
}
if (showRes)
printf(" resolution: %10ld.%09ld\en",
(long) ts.tv_sec, ts.tv_nsec);
}
int
main(int argc, char *argv[])
{
bool showRes = argc > 1;
displayClock(CLOCK_REALTIME, "CLOCK_REALTIME", showRes);
#ifdef CLOCK_TAI
displayClock(CLOCK_TAI, "CLOCK_TAI", showRes);
#endif
displayClock(CLOCK_MONOTONIC, "CLOCK_MONOTONIC", showRes);
#ifdef CLOCK_BOOTTIME
displayClock(CLOCK_BOOTTIME, "CLOCK_BOOTTIME", showRes);
#endif
exit(EXIT_SUCCESS);
}
.EE
.SH SEE ALSO
.BR date (1),
.BR gettimeofday (2),