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

First attempt, an experiment

After editing the .plist I tried logging out of the system, then logging in. This did not have the desired effect.

Second attempt

Maybe not the best approach for modern releases of the system, these two commands seem effective:

/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill

/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -seed -v

• option -v only if you want a verbose view of progress.

After the scan completes — after the Launch Services database has been seeded — you should find that .sh files open in Terminal in response to an open command.

Probably best

The accepted answer to Super User question Is there a faster way to change default apps associated with file types on OS X? suggests:

… restarting the OS to apply changes (logging out and back in isn't enough) …

This grey area leads to a new question —

Why is a command line change to ~/Library/Preferences/com.apple.LaunchServices.plist not effective immediately?

An accepted answer to that question should allow us to refine answers here.

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.