sleep - suspend execution for an interval of time
The sleep(1) command suspends execution for a minimum of seconds. The sleep(1) command is used to schedule the execution of other commands (see EXAMPLES).
The sleep(1) utility exits with one of the following values:
To schedule the execution of a command for 1800 seconds later, use:
This invocation would wait a half hour before running the script command_file.
(sleep 1800; sh command_file >& errors)&