xref: /freebsd/bin/sleep/sleep.1 (revision d46d907a26310881241683862e674f0f2284eb53)

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.\"	@(#)sleep.1	8.3 (Berkeley) 4/18/94
.\" $FreeBSD$
.\"
.Dd May 25, 2022
.Dt SLEEP 1
.Os
.Sh NAME
.Nm sleep
.Nd suspend execution for an interval of time
.Sh SYNOPSIS
.Nm
.Ar number Ns Op Ar unit
.Ar ...
.Sh DESCRIPTION
The
.Nm
command suspends execution for a minimum of
.Ar number
seconds (the default, or unit
.Cm s ) ,
minutes (unit
.Cm m ) ,
hours (unit
.Cm h ) ,
or days (unit
.Cm d ) .
If multiple arguments are passed, the delay will be the sum of all values.
.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 supports other time units than seconds,
honors a non-integer number of time units to sleep in any form acceptable by
.Xr strtod 3 ,
and accepts more than one delay value.
These are non-portable extensions, but they have also been 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 .