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.\"     From: @(#)ualarm.3	8.2 (Berkeley) 4/19/94
.\" $FreeBSD: src/lib/libc/gen/ualarm.3,v 1.9.2.5 2001/12/14 18:33:51 ru Exp $
.\"
.Dd February 17, 2021
.Dt UALARM 3
.Os
.Sh NAME
.Nm ualarm
.Nd schedule signal after specified time
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft useconds_t
.Fn ualarm "useconds_t microseconds" "useconds_t interval"
.Sh DESCRIPTION
.Bf -symbolic
This is a simplified interface to
.Xr setitimer 2 .
.Ef
.Pp
The
.Fn ualarm
function
waits a count of
.Ar microseconds
before asserting the terminating signal
.Dv SIGALRM .
System activity or time used in processing the call may cause a slight
delay.
.Pp
If the
.Fa interval
argument is non-zero, the
.Dv SIGALRM
signal will be sent
to the process every
.Fa interval
microseconds after the timer expires (e.g. after
.Fa value
microseconds have passed).
.Pp
Due to
.Xr setitimer 2
restriction the maximum number of
.Ar microseconds
and
.Ar interval
is limited to 100000000000000
(in case this value fit in the unsigned integer).
.Sh RETURN VALUES
When the signal has successfully been caught,
.Fn ualarm
returns the amount of time left on the clock.
.Sh NOTES
A microsecond is 0.000001 seconds.
.Sh SEE ALSO
.Xr getitimer 2 ,
.Xr setitimer 2 ,
.Xr sigaction 2 ,
.Xr sigsuspend 2 ,
.Xr signal 3 ,
.Xr sleep 3 ,
.Xr usleep 3
.Sh HISTORY
The
.Fn ualarm
function appeared in
.Bx 4.3 .