For those who don't already know, in Rails 2.0, the .rhtml and .rxml file extensions will be deprecated in favor of the .erb and .builder extensions. This is being done to make a distinction between the MIME type of the file and the renderer. For example, what was once index.rhtml will now be index.html.erb, to indicate a MIME type of html, and a renderer of erb. Likewise, index.rxml might now be index.xml.builder. See the changeset for more information on why, if you're interested.

So, how about renaming all your rhtml view files in an existing project to comply with the new convention? My ghetto bash skills to the rescue. From the root of your Rails app:

myapp$ for old in `find app/views -name *.rhtml`; do svn mv $old `dirname $old`/`basename $old .rhtml`.html.erb; done

Of course, the world doesn't run on OS X and Linux alone. Luckily, our friend Ruby is cross-platform. So, alternatively:

c:\myapp> ruby -e "Dir[\"app/views/**/*.r*\"].each { |f| puts `svn mv #{f} #{$1}.html.erb` if f =~ /^(.+)\.rhtml$/ }"

One note — your app has to be under subversion source control for this to work. If not, you'll have to change the "svn mv" part to a simple "mv" or "copy" command, based on your platform.

And of course, you don't have to do this. The .rhtml extension will still work. But, of course, we want to be cool and stick with the conventions.

Update: Fixed a typo in the Ruby one-liner.

Update 2: Our example here only renames your .rhtml files to .html.erb. For a more useful approach, try this rake task (thanks Jamie), which takes care of rhtml, rxml, and rjs. Better still, you can use sake (thanks topfunky) and make a single command that will do the job across all your projects.