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.\" $OpenBSD: alarm.3,v 1.15 2016/01/28 22:11:39 jmc Exp $
.\"
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.Dd $Mdocdate: January 28 2016 $
.Dt ALARM 3
.Os
.Sh NAME
.Nm alarm
.Nd set signal timer alarm
.Sh SYNOPSIS
.In unistd.h
.Ft unsigned int
.Fn alarm "unsigned int seconds"
.Sh DESCRIPTION
.Bf -symbolic
This is a simplified interface to
.Xr setitimer 2 .
.Ef
.Pp
The
.Fn alarm
function waits a count of
.Ar seconds
before asserting the terminating signal
.Dv SIGALRM .
When the signal has successfully been caught,
.Fn alarm
returns the amount of time left on the clock.
The maximum number of
.Ar seconds
allowed
is 100000000.
.Pp
If an alarm has been set with
.Fn alarm ,
another call to
.Fn alarm
will supersede the prior call.
The request
.Fn alarm "0"
voids the current
alarm.
.Sh RETURN VALUES
If the call succeeds, any time left remaining from a previous call is returned.
If an error occurs, the value \-1 is returned, and a more precise
error code is placed in the global variable
.Va errno .
.Sh SEE ALSO
.Xr setitimer 2 ,
.Xr sigaction 2 ,
.Xr sigsuspend 2 ,
.Xr signal 3 ,
.Xr sleep 3 ,
.Xr ualarm 3
.Sh STANDARDS
The
.Fn alarm
function conforms to
.St -p1003.1-2008 .
.Sh HISTORY
An
.Fn alarm
system call appeared in the Programmer's Workbench (PWB/UNIX)
and was ported to
.At v7 .
For
.Bx 4.1c ,
it was reimplemented as a wrapper around the
.Xr setitimer 2
system call.
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