at - schedule a command, but only once

You may also want to launch a command at a given day, but not regularly. For
example, you want to be reminded an appointment, today at 6pm. You run X, and
you'd like to be notified at 5:30pm, for example, that you must go. at is
what you want here:

$ at 5:30pm
  # You're now in front of the "at" prompt
at> xmessage "Time to go now! Appointment at 6pm"
  # Type C-d to exit
at> <EOT>
$

You can specify the time in different manners:


now +: Means, well, now, plus an interval (optionally. No interval
specified means just now). The syntax for the interval is:

   (minutes|hours|days|weeks|months)

For example, you can specify now + 1 hour, now + 3 days and so on.

  - Fully specify the date. The  parameter is mandatory.
at is very liberal in what it accepts: you can for example type 0100,
04:20, 2am, 0530pm, 1800, or one of three special values: noon, teatime (4pm)
or midnight. The  parameter is optional. You can specify it in different
manners as well: 12/20/2001 for example, which stands for December 20th, 2001
or, the European way, 20.12.2001. You may omit the year, but then only the
European notation is accepted: 20.12. You can also specify the month in
full letters: Dec 20 or 20 Dec are both valid.

Options:

  -l     - Prints the list of currently queued jobs; the first field is the
           job number. This is equivalent to the atq command.
  -d  - Remove job number  from the queue. You can obtain job numbers
           from atq. This is equivalent to atrm