Archive for August 2012

Using IRC to set Reminders with the “at” Command

reminder

Remind me at 5pm to go to the bank

You can use IRC to remind you to do anything. Now that you have a directory that your IRC bot reads, you can use one of Linux’s best kept secrets: the at command. The at command allows you to schedule one-time jobs to be run in the future — a non-reoccurring cronjob. The real win with using at is its time syntax. Here’s a few examples from the man page:

  • to run a job at 4pm three days from now, you would do at 4pm + 3 day
  • to run a job at 10:00am on July 31, you would do at 10am Jul 31
  • to run a job at 1am tomorrow, you would do at 1am tomorrow.

You can use this to run any command or script at a given time. This makes the at command perfect for usage over IRC — we just need to drop a file with the reminder in the /say directory at the given time. It’s easy to wrap some of this syntax to give the reminder command a human-like syntax.

Syntax

I went with the following syntax, best expressed with a summarized version of the regular expression used to parse it:

 ^(remind|pm) (me|us|everyone) (at|in|on) (.*?) to (.*)$

You might say the following things in the IRC channel to the bot:

  • remind me in 5 minutes to check the dryer
  • pm me at 10pm to remember to charge my cell phone
  • remind everyone on august 1s to enjoy the weather

These commands all get sent to at. Behind the scenes, the bot does the following:

  1. creates a file under /var/tmp with the contents of the reminder. The filename follows the format mentioned in the Mixing the Command-Line and IRC post, and sets the unique identifier to a hash of the submitter’s nick and current timestamp.
  2. the at command is instructed to move the file from /var/tmp/ to the ~/say directory at the requested time
  3. at the requested time, at moves the file and the bot picks it up and prints it to the channel.

There’s only a small amount of additional wrapping needed to make the interaction fluid. The biggest abstraction is in the difference between the “remind me at/on” and “remind me in” commands. “remind me at/on” passes the date straight through to the at command, where “in” prepends “now +” to the request. That’s it!

The channel has been using the reminder feature more and more. It’s nice to set a reminder with a long article you’d like to read, or set a reminder in 2 weeks to write a blog post for the DeadCoderSociety. Socializing reminders is a great way to increase community interaction and raise awareness for interesting information that might otherwise end up on a sticky note in a pocket somewhere.

Bonus:

The other Friday I was talking about payday and one guy had added a reminder to “GET PAID” for the next set of pairs of weeks. We ended up adding this on the command-line:

for i in `seq 12 2 50`; do
    echo 'echo "GET PAID" > /srv/git/neilforobot/say/#dcs@paid' | 
    at now + $i weeks ; 
done

At makes setting these types of reminders up easy!