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List:       linux-man
Subject:    timespec_get() part of C11
From:       Walter Harms <wharms () bfs ! de>
Date:       2021-04-24 17:41:42
Message-ID: f79cbb6ecda24a1e90fb3c242d97c218 () bfs ! de
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.ds N1 The example is simplified code and not production ready.
.de N2 
.SH COLOPHON
This page is part of release 4.16 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
..

.TH timespec_get  1 "2021-04-20" Linux "User Manuals"
.SH NAME
timespec_get  \- get time in high resolution
.SH SYNOPSIS
.B #include <time.h>
.PP
.BI "int timespec_get( struct timespec *"ts ", int " base  ");"
.SH DESCRIPTION
The function 
.B timespec_get()
will fill 
.I ts
wth the current time. The argument is a 
.I struct timespec
what is specified like:
.nf
struct timespec
{
   time_t tv_sec;     /* Seconds.  */
   long tv_nsec;   /* Nanoseconds.  */
};
.fi
The elements of the struct hold the seconds and nanoseconds since epoch.
The system clock will round the nanosecond argument.
.PP
The second argument
.B base
indicate the time base.  POSIX requieres 
.I TIME_UTC
only.  All  others are implementation defined.
.SH RETURN VALUE
The function will return 
.I base 
or 0 for failure.
.SH EXAMPLE
The example program will show the current time
in YYYY-MM-DD hh:mm:ss and then the nanoseconds .
.EX
/* compile with:
 *  gcc timespec.c -o timespec
 */
#include <stdio.h>
#include <time.h>
 
int main(void)
{
    struct timespec ts;
    char buf[30];
    timespec_get(&ts, TIME_UTC);
    strftime(buf, sizeof(buf), "%F %T", gmtime(&ts.tv_sec));
    printf("Current time: %s ", buf);
    printf("UTC and %ld nsec\\n", ts.tv_nsec);
    return (0);
}
.EE
\*(N1
.SH NOTE
This function is equal to the POSIX function 
.BR "clock_gettime(CLOCK_REALTIME, ts)" .
.PP
The ts.tv_sec is equal to the return value of
.BR time(NULL) .
.SH "CONFORMING TO"
The function is a C11 requirement and appears first time in 
.BR "glibc 2.16 " .
.SH "SEE ALSO"
.BR clock_gettime(3) ,
.BR time (2),
.BR time (7)
\*(N2
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