Everybody knows cron jobs, right? But not everybody knows its sibling at.

As you might anticipate, if cron is used to schedule tasks that are repeated periodically, Linux must have something else to schedule one-time tasks, and this is at.

I “discovered” at when I wrote a Pomodoro timer in bash, and I periodically went back to it. One of this times, I got struck by this nice use case described in its readme (Courtesy of tldr)

$ tldr at
 at Executes commands at a specified time. More information: <https://man.archlinux.org/man/at.1>.
 - echo
     "notify-send 'Wake up!'" | at 11pm Feb 18

I know this is equivalent to any calendar notification, but spending most of my time in a Terminal and not wanting to pollute my calendar with silly reminders, I found this idea quite intriguing.

Moreover, at supports smart dates like “tomorrow”, “5pm next week”, “next month” and so on, like the new shiny fancy reminder apps!

So, what is it missing then?

  1. I don’t want to write the notify-send part of the command every time
  2. I want to delete a specific reminder
  3. I want to show a list of all the reminders set

Point just 1 needs a wrapper, some easy script (I called it rem) that crafts the actual command line to pass to at.

For example the following:

$ cat rem
#!/usr/bin/env bash
echo "notify-send \"$@\""

Which I can then pass to at to set the reminder

$ rem buy the milk | at 5pm

Actually, not all smart dates are super easy in at. For example, if I want a reminder to fire in 30 minutes, the syntax is

$ at now + 30 minutes

not bad, but what if I set alias in="at now +" in my .bashrc? Now it is much better:

$ rem buy the milk | in 30 minutes

So, back to the point, we can set any reminder now, but how to delete or list them? at is well equipped with atq and atrm commands.

  • atq shows a list of the jobs with their ID and time
  • atrm deletes a job by ID
$ atq
1       Mon Apr  1 17:57:00 2024 a carlo
$ atrm 1

This is already good and I don’t feel the urge to write any wrapper around it.

However, atq it only shows the job, not the message, so I cannot see the reminder message associated.

This last requirements needs some more work. Basically looping over the jobs and extracting the message from the job content, but I had fun and pushed a little more into the script getting the message together with the time of execution and the time left.

$ rem
- Apr/13/2024 17:39/0h:17m (6) call dad
- Apr/13/2024 18:00/0h:38m (7) buy the milk
- Apr/14/2024 20:00/01d (5) take out the trash

You can see and use the resulting app at https://github.com/clobrano/rem.

Bottom line: Linux is full of useful utilities, and it is often enough just to combine them to get nice results and some fun.