Let's show an example of how a MonkeyCI build script could look like:

(ns build
  (:use [monkey.ci.build.v2]))

(action-job
 "test-job"
 (fn [_]
   (println "Hi, I don't do very much.  But it's a start!")))

This very basic (and, frankly, useless) build script defines a single job that will be executed by MonkeyCI if you put it in your repository at /.monkeyci/build.clj.

Commit the file to your repository, push it to Github or Bitbucket and log in at MonkeyCI. If it's your first time, a new user will automatically be created and you can also create a new customer, or join an existing one. Go ahead, it's free!

So, let's analyze the above file line by line.

(ns build
  (:use [monkey.ci.build.v2]))

This is the namespace declaration and tells the script processor to include the v2 namespace for MonkeyCI builds. This is currently the most recent version of the build API and is something you will most likely do in every build script. It contains the most basic functionality for setting up a build script in MonkeyCI. There are other ways to include a namespace, but use is the simplest one. It makes all functions in the target namespace invokable from your script file. Although it's advised to use an alias for clarity, we'll go without one in this example, because it's such a simple file. But see the documentation for the use expression when you have time.

Although you're not required to create a new namespace called build, it's the cleanest way. Generally the name of the file should be the same as the namespace it holds, and it will be necessary if you want to write unit tests, but more on that later.

(action-job

This declares an action job. There are two kinds of jobs in MonkeyCI: action jobs and container jobs. The first type just runs an arbitrary function in your script, while the second type starts a new container job. Most of the time you will probably use container jobs, but especially in the more complicated build scripts, action jobs may pop up as well. They are especially well suited to do some intermediate processing that you would otherwise have to write a clunky shell script for. Think of parsing JSON documents, composing HTTP requests, and so on. Note that these action jobs run inside the Clojure process, so you have access to all functionality available to the build script, and you can even execute shell scripts as well! We'll talk later on how to include additional libraries in your build to broaden the scope even further.

 "test-job"

This is the identifier of that specific job. Each identifier should be unique over your build script, and it is used to display information, but also to declare dependencies between jobs. We advise to keep the name short but descriptive. You can include every character in the name, and there is no real limit to it's length, but let's say 16MB is about the practical maximum length, due to database storage limitations.

 (fn [_]
   (println "Hi, I don't do very much.  But it's a start!")))

This is the actual function that will be executed. It is passed the script context as an argument, but since we're not using it here, we're replacing it with an _. This means more or less "I know this function receives an argument, but we're not using it right now." In this case, it just prints a message. This message will be displayed when you navigate in the application site to that specific job.

Conclusion

The above example illustrates in a nutshell how MonkeyCI builds work. If this triggers your curiosity, you can learn more by proceeding to one of the related articles.