Use custom command to open files

gedit application is set as default application for text files. Supposing I have a script with execution rights in /usr/bin, how can I set that script to be run when I open a text file using Nautilus or xdg-open?

/usr/bin/foo:

echo "Works!"
gedit $*

If I do foo my_text_file, then Works! message will appear and gedit will run. How can I set this foo script to be run as default application?

The clean way would be to create a .desktop file for your script and then make it the default text editor.

1. Create a file called /usr/share/applications/foo.desktop with the following contents:

   [Desktop Entry]
   Name=foo
   Exec=/usr/bin/foo.sh %U
   Terminal=false
   Type=Application
   MimeType=text/plain;
   

2. Make it the default program for the text/plain mimetype:

   xdg-mime default foo.desktop "text/plain" 
   

As a dirty hack you could also simply call your script gedit:

sudo mv /usr/bin/gedit /usr/bin/gedit.orig
sudo mv /path/to/yourscript.sh /usr/bin/gedit

Then make your script call the original:

echo "Works!"
/usr/bin/gedit.original "$@"