TL;DR: Some times you just want to do something and have one file of source code for that task. lein-script sets that up for you in Clojure.

Back in the dark twilight days of the old millenium, after years of programming C and FORTRAN, I discovered Perl. I loved how easy it became to automate so many common tasks with just a few lines of code. I wrote Perl modules so often that eventually I wrote a Perl script, perlscript, to generate Perl scripts ā€“ i.e. to create files with the correct shebang preamble, add the use strict declaration, set file permissions, add my name and copyright info, etc.

The sixty seconds or so of time saved for each script I made paid for the minor cost of writing perlscript many times over. When I switched to Python, I did the same thing with a script I called pyscript, and I happily used that for awhile (until I started packaging everything up with distutils).

As of this year Iā€™m developing more or less exclusively in Clojure. One thing that irritated me a bit when I started with the language was the need to create a whole Leiningen project just to automate some simple task.

That irritation went away recently when I discovered lein-exec, a Leiningen plugin which lets one create single-file scripts and execute them without need of a project.clj, source sub-directory, etc.

However, I still wanted to be able to spin out new scripts quickly. So I wrote a Leiningen template lein-script which does this:

$ lein new script foo
Generating stand-alone script "foo".
$ ./foo
Welcome to foo!

The generated script contains a commented-out example dependency declaration for lein-exec which shows how to introduce and use external libraries. The process is surprisingly easy ā€“ it even works fine for me with Emacs and nREPL.

Pushed to Clojars and GitHub. (You need to update .lein/profiles.clj as shown in the GitHub project for this to work.)

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16 February 2014