sleep does nothing, for a certain amount of time. That amount of time may be specified in several ways:
Sleep for five seconds:
Sleep for five minutes:
Sleep for one minute and 23 seconds:
Sleep for half a second:
Sleep for a minute and a half:
Sleep for one minute, 23.45 seconds:
Sleep until nine o'clock tonight:
sleep -until 21:00
Sleep until a quarter of a second past nine o'clock tonight:
sleep -until 21:00:00.25
The default colon-separated format for relative sleeps is mm:ss, but for absolute (-until) sleeps it's hh:mm, which is irregular and potentially confusing.
If you try to use the -until option to sleep until some time tomorrow (if, for example, at 11:00 at night you invoke ``sleep -until 1:00'', intending about a two-hour sleep) the program instead complains that it can't sleep for a negative time.
This is obviously a reimplementation,
of the standard
See http://www.eskimo.com/~scs/src/#sleep for possible updates.
Steve Summit, firstname.lastname@example.org