Linux Schedule

People schedule things for all sorts of reason. There’s school schedules, lunch schedules… I bet Iron Man has a schedule for cleaning his suit. Which makes me wonder, what does Iron Man do for a bathroom if he’s in the suit for a long time?

Anyway, back to scheduling. Suppose I want my computer to make a beep in two hours to remind me to go watch The Avengers.It’s very important that I start watching in two hours because I want to follow it up with The Avengers: Age of Ultron and then I want to go have dinner and see Infinity War.

The Avengers!

I want my computer to make a beep in two hours. The first question is, how do I make my computer beep?

One way to do it is by this:

Alpha:~ computerlamp$ echo -en "\a"

That’s a lot to remember, isn’t it? Let’s use nano and make a file we’ll call beep.sh

Here’s a picture of me making the file:

Making beep.sh

Remember, when you save it, call it beep.sh

The next thing to do is to change the permissions on the file. We want this to be executable.

Alpha:~ computerlamp$ chmod 755 beep.sh

Now we’ve made our first shell script. A shell script is a computer program that executes shell commands in the order that they’re in the file. So if we run beep.sh like this:

Alpha:~ computerlamp$ ./beep.sh

we’ll get a beep! You’ve now written a computer program. How cool is that?

Now the next problem is how do we schedule this?

We use a program called at. I know, that’s a boring name. Now it’s 11 am and I want the computer to beep me at 1pm.

Alpha:~ computerlamp$ at -f /home/computerlamp/beep.sh 01:00PM

Now my computer knows that at 1PM it should run the program beep.sh, which means my computer will beep at me then.

How does this work? Well, there’s a daemon called atd that runs these jobs.

What if I want to run something every hour on the hour? I want to make my own cuckoo clock by making my computer beep at me every hour. We’ll talk about how tod o that next time.