freebsd-dev/bin/sleep/sleep.1

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.\"	@(#)sleep.1	8.3 (Berkeley) 4/18/94
.\" $FreeBSD$
.\"
.Dd April 18, 1994
.Dt SLEEP 1
.Os
.Sh NAME
.Nm sleep
.Nd suspend execution for an interval of time
.Sh SYNOPSIS
.Nm
.Ar seconds
.Sh DESCRIPTION
The
.Nm
command
suspends execution for a minimum of
.Ar seconds .
.Pp
If the
.Nm
command receives a signal, it takes the standard action.
.Sh IMPLEMENTATION NOTES
The
.Dv SIGALRM
signal is not handled specially by this implementation.
.Pp
The
.Nm
command will accept and honor a non-integer number of specified seconds
.Po
with a
.Ql .\&
character as a decimal point
.Pc .
.Bf Sy
This is a non-portable extension, and its use will nearly guarantee that
a shell script will not execute properly on another system.
.Ef
.Sh DIAGNOSTICS
The
.Nm
utility exits with one of the following values:
.Bl -tag -width flag
.It Li \&0
On successful completion.
.It Li \&>\&0
An error occurred.
.El
.Sh EXAMPLES
To schedule the execution of a command for
.Va x
number 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 the
.Xr at 1
utility.)
.Pp
To reiteratively run a command (with the
.Xr csh 1 ) :
.Pp
.Bd -literal -offset indent -compact
while (1)
	if (! -r zzz.rawdata) then
		sleep 300
	else
		foreach i (`ls *.rawdata`)
			sleep 70
			awk -f collapse_data $i >> results
		end
		break
	endif
end
.Ed
.Pp
The scenario for a script such as this 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,
when the file is found, then another portion processing
is done courteously by sleeping for 70 seconds in between each
awk job.
.Sh SEE ALSO
.Xr nanosleep 2 ,
.Xr sleep 3
.Sh STANDARDS
The
.Nm
command is expected to be
.St -p1003.2
compatible.