NAME

sleep — suspend execution for an interval of time

SYNOPSIS

sleep

seconds

DESCRIPTION

The sleep utility suspends execution for a minimum of seconds. It is usually used to schedule the execution of other commands (see EXAMPLES below).

Note: The NetBSD sleep command will accept and honor a non-integer number of specified seconds. This is a non-portable extension, and its use will nearly guarantee that a shell script will not execute properly on another system.

When the SIGINFO signal is received, the estimate of the amount of seconds left to sleep is printed on the standard output.

EXIT STATUS

The sleep utility exits with one of the following values:

0

On successful completion, or if the signal SIGALRM was received.

>0

An error occurred.

EXAMPLES

To schedule the execution of a command for 1800 seconds later:

(sleep 1800; sh command_file >& errors)&

This incantation would wait half an hour before running the script command_file. (See the at(1) utility.)

To reiteratively run a command (with csh(1)):

while (1) 
	if (! -r zzz.rawdata) then 
		sleep 300 
	else 
		foreach i (*.rawdata) 
			sleep 70 
			awk -f collapse_data $i >> results 
		end 
		break 
	endif 
end

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.

SEE ALSO

at(1), nanosleep(2), sleep(3)

STANDARDS

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