xref: /freebsd/bin/sleep/sleep.1 (revision 2295cae7e606d75016575927c3d8729745abb17a)

.\"-
.\" 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.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" 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
.\"    documentation and/or other materials provided with the distribution.
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd March 22, 2024
.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
.Op ...
.Sh DESCRIPTION
The
.Nm
command suspends execution for a minimum of
.Ar number
seconds (the default, or unit
.Li s ) ,
minutes (unit
.Li m ) ,
hours (unit
.Li h ) ,
or days (unit
.Li d ) .
Intervals can be written in any form allowed by
.Xr strtod 3 .
If multiple intervals are given, they are added together.
If the final sum is zero or negative,
.Nm
exits immediately.
.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.
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
To run a command after half an hour:
.Pp
.Dl (sleep 0.5h; sh command_file >out 2>err)&
.Pp
This incantation would wait half an hour before
running the script
.Pa command_file .
See the
.Xr at 1
utility for another way to do this.
.Pp
To reiteratively run a command:
.Pp
.Bd -literal -offset indent -compact
while :; do
	if ! [ -r zzz.rawdata ] ; then
		sleep 5m
	else
		for i in *.rawdata ; do
			sleep 70
			awk -f collapse_data "$i"
		done >results
		break
	fi
done
.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
.Pa zzz.rawdata
is created).
The script checks every five minutes for the file
.Pa zzz.rawdata ,
when the file is found, then another portion processing
is done courteously by sleeping for 70 seconds in between each
.Xr awk 1
job.
.Sh SEE ALSO
.Xr nanosleep 2 ,
.Xr sleep 3
.Sh STANDARDS
The
.Nm
command is expected to be
.St -p1003.2
compatible.
.Pp
Support for non-integer intervals, units other than seconds, and
multiple intervals which are added together are non-portable
extensions first introduced in GNU sh-utils 2.0a (released in 2002).
.Sh HISTORY
A
.Nm
command appeared in
.At v4 .