freebsd/bin/sleep/sleep.1

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.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 .