NAME

sleep — suspend execution for an interval of time

SYNOPSIS

DESCRIPTION

The sleep command suspends execution for a minimum of number seconds (the default, or unit s), minutes (unit m), hours (unit h), or days (unit d). Intervals can be written in any form allowed by strtod(3). If multiple intervals are given, they are added together. If the final sum is zero or negative, sleep exits immediately.

If the sleep command receives a signal, it takes the standard action. When the SIGINFO signal is received, the estimate of the amount of seconds left to sleep is printed on the standard output.

IMPLEMENTATION NOTES

The SIGALRM signal is not handled specially by this implementation.

EXIT STATUS

The sleep utility exits 0 on success, and >0 if an error occurs.

EXAMPLES

To run a command after half an hour:

This incantation would wait half an hour before running the script command_file. See the at(1) utility for another way to do this.

To reiteratively run a command:

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

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(1) job.

SEE ALSO

nanosleep(2), sleep(3)

STANDARDS

The sleep command is expected to be IEEE Std 1003.2 (“POSIX.2”) compatible.

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).

HISTORY

A sleep command appeared in Version 4 AT&T UNIX.