freebsd-dev/lib/libc/gen/alarm.3

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.\" Copyright (c) 1980, 1991, 1993, 1994
.\" The Regents of the University of California. All rights reserved.
.\"
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.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
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.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
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.\" @(#)alarm.3 8.2 (Berkeley) 4/19/94
.\"
.Dd April 19, 1994
.Dt ALARM 3
.Os BSD 4
.Sh NAME
.Nm alarm
.Nd set signal timer alarm
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft unsigned int
.Fn alarm "unsigned int seconds"
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.Sh DESCRIPTION
.Bf -symbolic
This interface is made obsolete by setitimer(2).
.Ef
.Pp
The
.Fn alarm
function sets a timer to deliver the signal
.Dv SIGALRM
to the calling process after the specified number of
.Fa seconds .
If an alarm has already been set with
.Fn alarm
but has not been delivered, another call to
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.Fn alarm
will supersede the prior call.
The request
.Fn alarm "0"
voids the current
alarm and the signal SIGALRM will not be delivered.
.Pp
Due to
.Xr setitimer 2
restriction the maximum number of
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.Ar seconds
allowed is 100000000.
.Sh RETURN VALUES
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.Pp
The return value of
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.Fn alarm
is the amount of time left on the timer from a previous call to
.Fn alarm .
If no alarm is currently set, the return value is 0.
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.Sh SEE ALSO
.Xr setitimer 2 ,
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.Xr sigaction 2 ,
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.Xr sigpause 2 ,
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.Xr sigvec 2 ,
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.Xr signal 3 ,
.Xr sleep 3 ,
.Xr ualarm 3 ,
.Xr usleep 3
.\" .Sh STANDARDS
.\" The
.\" .Fn alarm
.\" function conforms to
.\" .St -p1003.1-90 .
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.Sh HISTORY
An
.Fn alarm
function appeared in
.At v7 .