Dead simple scripts in Clojure
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 – 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 I’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 – 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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