Parsing Quoted Strings in Ruby

Posted by Mike Naberezny in Python,Ruby

Python has a nice module in the standard library called shlex that parses strings as a Unix shell would. Here’s a Python interpreter session demonstrating its usage:
```
>>> import shlex
>>> shlex.split('foo "bar baz" qux')
['foo', 'bar baz', 'qux']
```
It’s useful for creating your own mini-languages or external DSLs that need to parse quoted strings like the one shown above.

We recently built an inventory tracking application in Ruby that has a user interface for selecting search filters. To expose the same search capabilities as a web service, we created a simple query language. I was looking for an shlex equivalent in Ruby.

It turns out that the Ruby Standard Library has a module called Shellwords:
```
>> require 'shellwords'
=> true
>> Shellwords::shellwords('foo "bar baz" qux')
=> ["foo", "bar baz", "qux"]
```
Shellwords is a little less capable than shlex but handles the most common use case just fine. It’s a convenient solution for a problem that comes up too often.

Update: Ruby 1.8.7 has added the shortcut methods Shellwords.split and String#shellsplit. Very nice.

This entry was posted on Monday, April 28th, 2008 at 4:40 am and is filed under Python, Ruby.