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

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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"
.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
.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
.Ar seconds
allowed is 100000000.
.Sh RETURN VALUES
.Pp
The return value of 
.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.
.Sh SEE ALSO
.Xr setitimer 2 ,
.Xr sigaction 2 ,
.Xr sigpause 2 ,
.Xr sigvec 2 ,
.Xr signal 3 ,
.Xr sleep 3 ,
.Xr ualarm 3 ,
.Xr usleep 3
.\" .Sh STANDARDS
.\" The
.\" .Fn alarm
.\" function conforms to 
.\" .St -p1003.1-90 .
.Sh HISTORY
An
.Fn alarm
function appeared in 
.At v7 .