First and foremost this is a biased article. These are all my opinions, and come from my working experience.
Bash(or Posix shell)
If you’re working with *nix and can’t toss together a simple init.d script in 5 minutes, you haven’t done enough bash. It’s everywhere, and it should still be your first automation choice. It has a simple syntax, and is designed specifically to execute programs in a non-interactive manner. You’ll be annoyed that it lacks unit tests, and complex error handling, but its purpose built to automate administrative tasks.
This is the language that you will run into if you work in operations. There will be backup scripts, nagios tests, and a large collection of digital duck tape written by co-workers, that do very important jobs. Its syntax is ugly, and you may find yourself writing a eval to handle exceptions, but its everywhere. CPAN makes it fairly easy to get things done, and you can’t beat this for string handling.
This is the latin of the *nix world, and is basically portable assembly language. I refrain from writing C whenever possible, since I rarely need the raw performance, and the security and stability consequences are pretty severe. You should understand the syntax(its ALGO right), and be able to read a simple application. It would be great if you could submit a patch to a open-source project, but I would never turn down an ops hire because they didn’t know C well enough.
PHP more important than C?! Yep. Like perl its everywhere, people use it for prototyped webapps, and full blow production systems. Its another ALGO syntax language, except you can put together a simple web page in 2-3 minutes; its almost as magical as the Twilio API. You’ll find yourself poking at it on more than one occasion, so you might as well know what you’re doing.
Doing something with puppet or chef? You probably should know some ruby, and in fact it probably more important to know ruby than chef of puppet. Its relatively easy to pick up, and so many of the automation tools people love are written int it. As an extra bonus, you could write rails and sinatra apps. It’s good to have in your back pocket.
People love to love python, but the truth is that its a bit of a diva. Its a language that favors reading over writing, and has a very bloated standard library with lots of broken components(which is the right http library to use?). It wants to be a simpler perl, but I never find it as useful, and it always takes longer. I know a lot of companies say they want to use it as their “scripting” language, but in practice I’ve not seen the value(i stil want to rewrite everyones code).
These are DSLs for configuration management. They are supposed to be simple to learn, and if you can’t figure them out with a web browser and a few minutes, they are failing.
More ALGO syntax, and more prevalent in high scale web applications. Minimally you should be able to read this language, but its useful to be able to pound out a few lines of Java. It has many rich frameworks, and you’ll likely find it sneaking into your stack where you need something done fast. Also, it is really useful when it comes time to tune the JVM.
When I’ve run into it running someplace serious I’ll update its score.
You have to know SQL. You will work with SQL databases, and you will want to move things in and out of them. You may want to know a dialect like MySQL very well, but you should understand the basics, and at a minimum be able to join a few tables, or create an aggregate query.