SLEEP(1)

NAME
sleep - suspend execution for an interval of time

SYNOPSIS
sleep number[unit] ...

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). If multiple arguments are passed, the delay will be the sum of all values.

If the sleep command receives a signal, it takes the standard action. When the SIGUSR1 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.

The sleep command supports other time units than seconds, honors a non-integer number of time units to sleep in any form acceptable by 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).

EXIT STATUS

EXAMPLES
To schedule the execution of a command for x number seconds later (with csh(1)):

    (sleep 1800; sh command_file >& errors)&

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

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

    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

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
nanosleep(2), sleep(3)

STANDARDS
The sleep command is expected to be p1003.2 compatible.

HISTORY
A sleep command appeared in AT&T UNIX.