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.\" $NetBSD: timeval.3,v 1.12 2011/04/12 08:39:26 jruoho Exp $
.\"
.\" Copyright (c) 2010 The NetBSD Foundation, Inc.
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.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Jukka Ruohonen.
.\"
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.\" modification, are permitted provided that the following conditions
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.Dd April 12, 2011
.Dt TIMEVAL_TO_TIMESPEC 3bsd
.Os
.Sh NAME
.Nm TIMEVAL_TO_TIMESPEC ,
.Nm TIMESPEC_TO_TIMEVAL
.Nd time structures conversion macros
.Sh LIBRARY
.ds str-Lb-libbsd Utility functions from BSD systems (libbsd, \-lbsd)
.ds doc-str-Lb-libbsd \*[str-Lb-libbsd]
.Lb libbsd
.Sh SYNOPSIS
.In sys/time.h
(See
.Xr libbsd 7
for include usage.)
.Ft void
.Fn TIMEVAL_TO_TIMESPEC "struct timeval *tv" "struct timespec *ts"
.Ft void
.Fn TIMESPEC_TO_TIMEVAL "struct timeval *tv" "struct timespec *ts"
.Sh DESCRIPTION
The
.Va timeval
structure represents elapsed time, in whole seconds,
and the rest of the elapsed time in microseconds.
.Pp
The
.Va timespec
structure represents elapsed time, in whole seconds,
and the rest of the elapsed time in nanoseconds.
.Pp
A microsecond is equal to one millionth of a second,
1000 nanoseconds, or 1/1000 milliseconds.
To ease the conversions, the macros
.Fn TIMEVAL_TO_TIMESPEC
and
.Fn TIMESPEC_TO_TIMEVAL
can be used to convert between
.Em struct timeval
and
.Em struct timespec .
.Sh EXAMPLES
It can be stressed that the traditional
.Tn UNIX
.Va timeval
and
.Va timespec
structures represent elapsed time, measured by the system clock.
The following sketch implements a function suitable
for use in a context where the
.Va timespec
structure is required for a conditional timeout:
.Bd -literal -offset indent
static void
example(struct timespec *spec, time_t minutes)
{
	struct timeval elapsed;

	(void)gettimeofday(&elapsed, NULL);

	TIMEVAL_TO_TIMESPEC(&elapsed, spec);

	/* Add the offset for timeout in minutes. */
	spec->tv_sec = spec->tv_sec + minutes * 60;
}
.Ed
.Pp
A better alternative would use the more precise
.Xr clock_gettime 2 .
.Sh SEE ALSO
.Xr timeradd 3bsd
kc3-lang/libbsd/man/TIMESPEC_TO_TIMEVAL.3bsd

Commit

man/TIMESPEC_TO_TIMEVAL.3bsd
