mpapis/rvm-binary — pull request #1 by fnichol (2012-10-16 18:42:41+00:00)
Title: Ensure not_if gets runs as shell command, not Ruby code.

The conditional execution methods in a Chef resource have 2 modes: one that takes a string and one that takes a Ruby block. Here's the details:

> not_if and only_if attributes can be passed as strings or blocks.

> Strings are executed as a shell command. The attribute is true if the command returns 0.
> Blocks are Ruby code. The attribute is true if the result is true.

(From the [Resources](http://wiki.opscode.com/display/chef/Resources#Resources-ConditionalExecution) wiki page)

Good stuff, thanks for this!