I was recently trying to create a basic piece of Clojure code to play with “real-time” log file parsing by playing with futures. The longer term goal of the experiment is to be able to tail -f a log file pipe that into my Clojure log parser as input.

As I wasn’t sure exactly what I would need to be doing, I wanted an easy way to run some code quickly without having to rebuild the jars through Leiningen every time I wanted to try something, in a manner similar to the way I am thinking I will be using it if the experiment succeeds.

I created a file test_input with the following lines:

1 hello
2 test
3 abacus
4 qwerty
5 what
6 dvorak

With this in place, my goal was to be able to run something like cat test_file | parser_concept. After a bit of searching I found the lein-exec plugin for Leiningen, and after very minor setup I was able to start iterating with input piped in from elsewhere.

The first step was to open my profiles.clj file in my ~/.lein directory. I made sure lein-exec was specified in my user plugins as so:

{:user {:plugins [[lein-exec "0.2.1"]
                  ;other plugins for lein
                 ]}}

With this in place I just put the following line at the top of my script.clj file:

#!/usr/bin/env lein exec

I then changed the permissions of script.clj file to make it executable, I was able to run the following and have my code run against the input.

cat test_input | ./script.clj

I will be posting a follow up entry outlining my next step of experimenting with “processing” each line read in as a future.