How to add another script extension for syntax highlighting in gedit:
First step is to go to the following directory:
gz@osx~# cd /Applications/gedit.app/Contents/Resources/share/gtksourceview-2.0/language-specs
There you will find a bunch of *.lang files.
My goal was to add *.ksh extension with the same highlighting like *.sh so I edited sh.lang as follows:
Open the file and search for:
Then replace it with: