.\"	$OpenBSD: sleep.1,v 1.14 2007/02/06 20:07:15 jmc 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.
.\"
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.\" 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
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.\" 3. 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.
.\"
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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 the specified number of
.Ar seconds .
This number must be positive and may contain a decimal fraction.
.Nm
is commonly used to schedule the execution of other commands (see below).
.Sh EXAMPLES
Wait a half hour before running the script
.Pa command_file
(see also the
.Xr at 1
utility):
.Pp
.Dl (sleep 1800; sh command_file >& errors)&
.Pp
To repetitively run a command (with
.Xr csh 1 ) :
.Bd -literal -offset indent
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
.Pa zzz.rawdata
is created).
The script checks every five minutes for this file.
When it 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:
.Bd -literal -offset indent
while true; do
	ls -l file
	sleep 5
done
.Ed
.Sh DIAGNOSTICS
The
.Nm
utility exits with one of the following values:
.Pp
.Bl -tag -width flag -compact
.It Li \&0
On successful completion, or if the signal
.Dv SIGALRM
was received.
.It Li \&>\&0
An error occurred.
.El
.Sh SEE ALSO
.Xr at 1 ,
.Xr nanosleep 2 ,
.Xr setitimer 2 ,
.Xr alarm 3 ,
.Xr sleep 3 ,
.Xr usleep 3
.Sh STANDARDS
The
.Nm
command offers a superset of
.St -p1003.2
functionality.
The handling of fractional arguments is provided as an extension to the
specification.