.\"	$OpenBSD: sleep.1,v 1.9 1999/12/06 20:27:38 espie Exp $
.\"	$NetBSD: sleep.1,v 1.9 1995/07/25 19:37:43 jtc Exp $
.\"
.\" Copyright (c) 1990, 1993, 1994
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 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.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\"
.\"	@(#)sleep.1	8.3 (Berkeley) 4/18/94
.\"
.Dd April 18, 1994
.Dt SLEEP 1
.Os
.Sh NAME
.Nm sleep
.Nd suspend execution for an interval of time
.Sh SYNOPSIS
.Nm sleep
.Ar seconds
.Sh DESCRIPTION
The
.Nm
utility
suspends execution for a minimum of
.Ar seconds .
.Nm
is used to schedule the execution of other commands (see
.Sx EXAMPLES
below).
.Pp
The
.Nm
utility exits with one of the following values:
.Bl -tag -width flag
.It Li \&0
On successful completion, or if the signal
.Dv SIGALRM
was received.
.It Li \&>\&0
An error occurred.
.El
.Pp
.Nm 
handles fractional arguments as an extension to
.St -p1003.2 .
.Sh EXAMPLES
To schedule the execution of a command for
.Va x
seconds later:
.Pp
.Dl (sleep 1800; sh command_file >& errors)&
.Pp
This incantation would wait a half hour before
running the script command_file (see also the
.Xr at 1
utility).
.Pp
To repetitively run a command (with
.Xr csh 1 ) :
.Pp
.Bd -literal -offset indent -compact
while (! -r zzz.rawdata) 
	sleep 300
end
foreach i (*.rawdata)
	sleep 70
	awk -f collapse_data $i >> results
end
.Ed
.Pp
The scenario for such a script might be: a program currently
running is taking longer than expected to process a series of
files, and it would be nice to have another program start 
processing the files created by the first program as soon as it is finished 
(when zzz.rawdata is created).
The script checks every five minutes for the file zzz.rawdata.
Then, when the file is found, processing is done in several steps
by sleeping 70 seconds between each
.Xr awk 1
job.
.Pp
To monitor the growth of a file without consuming too many resources :
.Pp
.Bd -literal -offset indent -compact
while true; do
	ls -l file
	sleep 5
done
.Ed
.Sh SEE ALSO
.Xr at 1 ,
.Xr setitimer 2 ,
.Xr alarm 3 ,
.Xr sleep 3
.Sh STANDARDS
The
.Nm
command offers a superset of
.St -p1003.2
functionality.