freebsd man page for sleep

SLEEP(1)						    BSD General Commands Manual 						  SLEEP(1)

NAME
     sleep -- suspend execution for an interval of time

SYNOPSIS
     sleep seconds

DESCRIPTION
     The sleep command suspends execution for a minimum of seconds.

     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.

     The sleep command allows and honors a non-integer number of seconds to sleep in any form acceptable by strtod(3).	This is a non-portable
     extension, and its use will nearly guarantee that a shell script will not execute properly on another system.

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

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 IEEE Std 1003.2 (``POSIX.2'') compatible.

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

BSD
								  April 18, 1994							       BSD