timeradd(3) — Linux manual pages

Linux manual pages	Section 3: Subroutines

Name

timeradd, timersub, timercmp, timerclear, timerisset — timeval operations

Synopsis

#include <sys/time.h>

`void timeradd(`	struct timeval *`a`,
	struct timeval *`b`,
	struct timeval *`res)`;

`void timersub(`	struct timeval *`a`,
	struct timeval *`b`,
	struct timeval *`res)`;

void timerclear( struct timeval *tvp);

int timerisset( struct timeval *tvp);

`int timercmp(`	struct timeval *`a`,
	struct timeval *`b`,
	`CMP)`;

Note

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
All functions shown above:
`_BSD_SOURCE`

DESCRIPTION

The macros are provided to operate on timeval structures, defined in <sys/time.h> as:

struct timeval {

time_t tv_sec;
/* seconds */

suseconds_t tv_usec;
/* microseconds */

};

timeradd() adds the time values in a and b, and places the sum in the timeval pointed to by res. The result is normalized such that res−>tv_usec has a value in the range 0 to 999,999.

timersub() subtracts the time value in b from the time value in a, and places the result in the timeval pointed to by res. The result is normalized such that res−>tv_usec has a value in the range 0 to 999,999.

timerclear() zeros out the timeval structure pointed to by tvp, so that it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC).

timerisset() returns true (nonzero) if either field of the timeval structure pointed to by tvp contains a nonzero value.

timercmp() compares the timer values in a and b using the comparison operator CMP, and returns true (nonzero) or false (0) depending on the result of the comparison. Some systems (but not Linux/glibc), have a broken timercmp() implementation, in which CMP of >=, <=, and == do not work; portable applications can instead use

!timercmp(..., <) !timercmp(..., >) !timercmp(..., !=)

RETURN VALUE

timerisset() and timercmp() return true (nonzero) or false (0).

ERRORS

No errors are defined.

CONFORMING TO

Not in POSIX.1-2001. Present on most BSD derivatives.

COLOPHON

This page is part of release 3.52 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man−pages/.

  Copyright (c) 2007 by Michael Kerrisk <mtk.manpagesgmail.com>

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2007-07-31, mtk, Created

struct	timeval {
	time_t	`tv_sec`;	/* seconds */
	suseconds_t	`tv_usec`;	/* microseconds */
};