How can I replace all \r\n with \n using Komodo Edit

There is actually a built-in feature for this in Komodo, but it's hard to find.

Right-click the Edit tab select Current File Settings. Under File Settings, change "Line Endings" to UNIX (\n) and de-select "Preserve existing line endings".

This is fine for individual files, but it would be a bit of a hassle if you were trying to do several files as a batch. For that, you could wrap some of swatso33's suggestions into a saved command using interpolation shortcuts.

UPDATE (2014-10-13): There is now an option: Clean Line Endings under the Code tab.

You can do this with either perl or sed using:

 perl -pe 's/\r?\n|\r/\r\n/g' inputfile > outputfile  # Convert to DOS.
 perl -pe 's/\r?\n|\r/\n/g'   inputfile > outputfile  # Convert to UNIX.
 sed -e 's/$/\r/' inputfile > outputfile              # UNIX to DOS  (adding CRs on Linux based OS that use GNU extensions).
 sed -e 's/\r$//' inputfile > outputfile              # DOS  to UNIX (removing CRs on Linux based OS that use GNU extensions).
 perl -pe 's/\r?\n|\r/\r/g'   inputfile > outputfile  # Convert to old Mac.

Code snippet is from http://en.wikipedia.org/wiki/Newline#Conversion_utilities