freebsd-dev/bin/sleep/sleep.1

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.\"	@(#)sleep.1	8.3 (Berkeley) 4/18/94
.\" $FreeBSD$
.\"
.Dd December 31, 2020
.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.
When the
.Dv SIGINFO
signal is received, the estimate of the amount of seconds left to
sleep is printed on the standard output.
.Sh IMPLEMENTATION NOTES
The
.Dv SIGALRM
signal is not handled specially by this implementation.
.Pp
The
.Nm
command allows and honors a non-integer number of seconds to sleep
in any form acceptable by
.Xr strtod 3 .
This is a non-portable extension, but is also implemented in GNU sh-utils
since version 2.0a (released in 2002).
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
To schedule the execution of a command for
.Va x
number seconds later (with
.Xr csh 1 ) :
.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.
.Sh HISTORY
A
.Nm
command appeared in
.At v4 .