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.\" Copyright (c) 2007 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%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.\" manual page may be incorrect or out-of-date.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
.\"
.\" 2007-07-31, mtk, Created
.\"
.TH TIMERADD 3 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
timeradd, timersub, timercmp, timerclear, timerisset \- timeval operations
.SH SYNOPSIS
.nf
.B #include <sys/time.h>
.PP
.BI "void timeradd(struct timeval *" a ", struct timeval *" b ,
.BI " struct timeval *" res );
.PP
.BI "void timersub(struct timeval *" a ", struct timeval *" b ,
.BI " struct timeval *" res );
.PP
.BI "void timerclear(struct timeval *" tvp );
.PP
.BI "int timerisset(struct timeval *" tvp );
.PP
.BI "int timercmp(struct timeval *" a ", struct timeval *" b ", " CMP );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
All functions shown above:
Since glibc 2.19:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_BSD_SOURCE
.SH DESCRIPTION
The macros are provided to operate on
.I timeval
structures, defined in
.I <sys/time.h>
as:
.PP
.in +4n
.EX
struct timeval {
time_t tv_sec; /* seconds */
suseconds_t tv_usec; /* microseconds */
};
.EE
.in
.PP
.BR timeradd ()
adds the time values in
.I a
and
.IR b ,
and places the sum in the
.I timeval
pointed to by
.IR res .
The result is normalized such that
.I res\->tv_usec
has a value in the range 0 to 999,999.
.PP
.BR timersub ()
subtracts the time value in
.I b
from the time value in
.IR a ,
and places the result in the
.I timeval
pointed to by
.IR res .
The result is normalized such that
.I res\->tv_usec
has a value in the range 0 to 999,999.
.PP
.BR timerclear ()
zeros out the
.I timeval
structure pointed to by
.IR tvp ,
so that it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC).
.PP
.BR timerisset ()
returns true (nonzero) if either field of the
.I timeval
structure pointed to by
.I tvp
contains a nonzero value.
.PP
.BR timercmp ()
compares the timer values in
.I a
and
.I b
using the comparison operator
.IR CMP ,
and returns true (nonzero) or false (0) depending on
the result of the comparison.
Some systems (but not Linux/glibc),
have a broken
.BR timercmp ()
implementation,
.\" HP-UX, Tru64, Irix have a definition like:
.\"#define timercmp(tvp, uvp, cmp) \
.\" ((tvp)->tv_sec cmp (uvp)->tv_sec || \
.\" (tvp)->tv_sec == (uvp)->tv_sec && (tvp)->tv_usec cmp (uvp)->tv_usec)
in which
.I CMP
of
.IR >= ,
.IR <= ,
and
.I ==
do not work;
portable applications can instead use
.PP
!timercmp(..., <)
!timercmp(..., >)
!timercmp(..., !=)
.SH RETURN VALUE
.BR timerisset ()
and
.BR timercmp ()
return true (nonzero) or false (0).
.SH ERRORS
No errors are defined.
.SH CONFORMING TO
Not in POSIX.1.
Present on most BSD derivatives.
.SH SEE ALSO
.BR gettimeofday (2),
.BR time (7)
.SH COLOPHON
This page is part of release 5.10 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/.
|
