What is a simple way to schedule a single event to happen at some time in the future?

Question

There are often times that I want my computer to do a single task, but not right now. For example, I could have it notify me in 30 minutes that it is time to leave work. Or maybe I want it to run a complicated test 2 hours from now when I'm sure most everyone else will be gone from the office.

I know I could create a cron job to run at a specific time of day, but that seems like a lot of work when all I want is something simple like "Run this script in 10 minutes", besides I'd have to figure out what time it will actually be X minutes/hours/days from now, and then delete the cron job once it finished.

Of course I could just write this script and run it in the background:

sleep X
do_task

But that just seems so clunky: I either need a new script for each task, or I need to write and maintain a script generic enough to do what I want, not to mention I have to figure out how many seconds are in the minutes, hours, or days I want.

Is there not an already established solution to this problem?

I'm guessing you've not run across [at](http://en.wikipedia.org/wiki/At_%28Unix%29) yet? — jw013, May 03 '12 at 00:09
this might seem very basic...but doesn't your system have any kind of calendar/todo list thing, with warnings? — JoséNunoFerreira, May 03 '12 at 12:23

score 27 · Accepted Answer · edited May 03 '12 at 03:19

27

I use a simple script with at:

#!/bin/bash
# email reminder notes using at(1)...

read -p "Time of message? [HH:MM] " time
read -p "Date of message? [dd.mm.yy] " date
read -p "Message body? " message

at "$time" "$date" <<EOF
echo "$message" | mailx -s "REMINDER" [email protected]
EOF

You could just as easily pipe the $message to notify-send or dzen if you wanted a desktop notification instead of an email.

edited May 03 '12 at 03:19

phunehehe

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answered May 03 '12 at 00:15

jasonwryan

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Can also use relative time (`+ 2 days`) and different formats (`YYYY-MM-DD`). Consult the manpage for more details. – Arcege May 03 '12 at 00:30
Yes: us antipodeans prefer DD-MM-YY :) – jasonwryan May 03 '12 at 04:01
I usually us at for quickie one off scripts. My favorite lazy way to schedule an at job is "now +5 minutes" which could also be hours or days. – George M May 03 '12 at 20:47
+1 for script and for mentioning dzen and notify-send which I had not heard of. – Joe May 05 '12 at 21:27
The dzen redirection isn't working for me. http://unix.stackexchange.com/q/38362/4143 – Cory Klein May 10 '12 at 22:22

score 6 · Answer 2 · answered May 03 '12 at 20:36

6

The generic way to use at is

Write a script that does what you want to do. Use the full path for all external commands, log output to a proper log-file or mail it.

Test the script.

Activate it with at -f YOURSCRIPT -t MMDDhhmm

answered May 03 '12 at 20:36

Nils

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What is a simple way to schedule a single event to happen at some time in the future?

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