OpenBSD-4.6/bin/sleep/sleep.1

.\"	$OpenBSD: sleep.1,v 1.17 2009/02/08 17:15:09 jmc Exp $
.\"	$NetBSD: sleep.1,v 1.9 1995/07/25 19:37:43 jtc Exp $
.\"
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.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
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.\"	@(#)sleep.1	8.3 (Berkeley) 4/18/94
.\"
.Dd $Mdocdate: February 8 2009 $
.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
utility is compliant with the
.St -p1003.1-2008
specification.
.Pp
The handling of fractional arguments is provided as an extension to that
specification.