To prefer Terminal to open .sh files — using the defaults command, without using Finder

In most cases, all that's required should be possible from the command line …

Preparation

Two commands:

defaults read com.apple.LaunchServices | grep -B 1 -A 3 public.shell-script

defaults read com.apple.LaunchServices | grep -B 1 -A 4 "LSHandlerContentTag = sh;"

If either command reveals an existing preference

Use Xcode or any other suitable property list editor to remove the relevant dictionary from the LSHandlers key within the following file:

~/Library/Preferences/com.apple.LaunchServices.plist

Hints:

• defaults, with which I'm more familiar, seems unsuitable for removal of a single dictionary from an array
• removal should be necessary only if (say) the user has previously used Finder to associate .sh files with an application other than the system default
• a Super User answer under How to change default app for all files of particular file type through terminal in OS X? is recently edited to include a script that uses PlistBuddy — credit to Daniel Beck.

Adding to LaunchServices preferences, for Terminal to view and edit .sh files

Two one-line commands.

Depending on your requirements, the first command alone may suffice:

defaults write com.apple.LaunchServices LSHandlers -array-add '{ LSHandlerContentType = "public.shell-script"; LSHandlerRoleViewer = "com.apple.Terminal"; LSHandlerRoleEditor = "com.apple.Terminal"; }'

defaults write com.apple.LaunchServices LSHandlers -array-add '{ LSHandlerContentTag = "sh"; LSHandlerContentTagClass = "public.filename-extension"; LSHandlerRoleViewer = "com.apple.Terminal"; LSHandlerRoleEditor = "com.apple.Terminal"; }'

For the new preferences to be respected

Modifications to the user domain persistence layer of Launch Services must be acknowledged. For this, least disruptive to the end user will be:

• a restart of the operating system.

From the command line, if immediate restart is acceptable:

sudo shutdown -r now

Background

Understanding Terminal.app support for .sh (public.shell-script)

Consider the result of the following command:

defaults read /Applications/Utilities/Terminal.app/Contents/Info

• under CFBundleDocumentTypes (an array of dictionaries describing the document types supported by the bundle) we see that Terminal is designed to support com.apple.terminal.shell-script

• public.shell-script (the system-declared UTI associated with .sh) is not supported at that level, it appears elsewhere in the property list — under UTExportedTypeDeclarations

Terminal aside for a moment: it's sometimes inappropriate (or simply worthless) to force opening of a document type, by an app that is designed without support for that type.

For Terminal, I imagine no harm in handling the public.shell-script type.