timespec_get() part of C11

timespec_get() part of C11

[Walter Harms]

.\" Copyright (c) 2021 wharms
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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

Re: timespec_get() part of C11

[Alejandro Colomar (man-pages)]

Hi Walter,

Thanks for the page!  Please see some comments below (I'll tell you more 
in the next iteration).

Cheers,

Alex

P.S.: How's it going with the other page you were working on? :)

On 4/24/21 7:41 PM, Walter Harms wrote:
> .\" Copyright (c) 2021 wharms
> .\" %%%LICENSE_START(VERBATIM)
> .\" Permission is granted to make and distribute verbatim copies of this
> .\" manual provided the copyright notice and this permission notice are
> .\" preserved on all copies.
> .\"
> .\" Permission is granted to copy and distribute modified versions of this
> .\" manual under the conditions for verbatim copying, provided that the
> .\" entire resulting derived work is distributed under the terms of a
> .\" permission notice identical to this one.
> .\"
> .\" Since the Linux kernel and libraries are constantly changing, this
> .\" manual page may be incorrect or out-of-date.  The author(s) assume no
> .\" responsibility for errors or omissions, or for damages resulting from
> .\" the use of the information contained herein.  The author(s) may not
> .\" have taken the same level of care in the production of this manual,
> .\" which is licensed free of charge, as they might when working
> .\" professionally.
> .\"
> .\" Formatted or processed versions of this manual, if unaccompanied by
> .\" the source, must acknowledge the copyright and authors of this work.
> .\" %%%LICENSE_END
> .\"
> .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

4.16? :)

> .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/.
> ..

You can remove the COLOPHON.   It is automatically created at release time.

> 
> .TH timespec_get  1 "2021-04-20" Linux "User Manuals"

Please, see `man 7 man-pages`, subsection 'Title line'.

> .SH NAME
> timespec_get  \- get time in high resolution

"high resolution" is relative.  It's like when you call Y is the "new 
X"... until it gets old.  I'd prefer expressing something like "get time 
in seconds and nanoseconds", don't you?

> .SH SYNOPSIS
> .B #include <time.h>
> .PP
> .BI "int timespec_get( struct timespec *"ts ", int " base  ");"

Don't add extra spaces inside the parentheses '( xxx', just like you'd 
do in normal english.
If there are no spaces, there's no need for using quotes: '");"' == ');'.
Also, use spaces to separate arguments to '.BI' always.

.BI "int timespec_get(struct timespec *" ts ", int " base );

> .SH DESCRIPTION
> The function
> .B timespec_get()
> will fill

No need to use future here.  'fills' is simpler.

> .I ts
> wth the current time. The argument is a

'The argument': I think I prefer to mention the argument name.

s/The argument /\n.I ts\n/?

> .I struct timespec
> what is specified like:
> .nf

Please, see `man 7 man-pages`, subsection 'Indentation of structure 
definitions, shell session logs, and so on'.

> struct timespec
> {
>     time_t tv_sec;     /* Seconds.  */
>     long tv_nsec;   /* Nanoseconds.  */

Please, align comments.

> };
> .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
> 


-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/