Comments on: How does Mac OS X know what program to open when you double click on a file?

Question: How does Mac OS X know what program to open when you double click on a file?

sammich — Tue, 31 Jan 2006 13:41:57 -0800

How does Mac OS X know what program to open when you double click on a file?

I'm sure there's some kind of database file somewhere that associates the file name extension or the resource fork with the application, but where is that file? And when I install or drag and drop an application to my drive, how or when does the app tell the Finder 'hey i'm here! I can open these sort of applications!'.

By: cillit bang

cillit bang — Tue, 31 Jan 2006 13:49:36 -0800

It's called Launch Services.

1) See the section above on the Launch Services database.
2) Applications are automatically registered just by being on your disk. Right click the app and choose "Show Bundle Contents". There's a file called info.plist that contains all the data.

By: tweebiscuit

tweebiscuit — Tue, 31 Jan 2006 13:57:39 -0800

From what I understand, OS X decides by both file extension AND metadata (which is why if you get a .doc from a friend who edited it in TextEdit, it will have TextEdit's icon, not Word's.) Not sure how the precedence works exactly, though. What I do know is that it makes it damn hard to get consistent results for every file of a particular type.

By: kindall

kindall — Tue, 31 Jan 2006 13:58:44 -0800

There are programs that can change this after the fact, by the way -- you can do it in the Finder, of course (by doing Get Info on a document, selecting the application that should open it, and clicking Change All). If you'd like to have full control over the Launch Services database in one place, install RCDefaultApp.

By: devilsbrigade

devilsbrigade — Tue, 31 Jan 2006 14:13:56 -0800

man 1 file

By: jxpx777

jxpx777 — Tue, 31 Jan 2006 14:50:00 -0800

If you are asking for the purpose of changing the program that opens the file, Select the file and select File> Get info. Then, under Opens with... select the program you want to use and then click the button below that says something to the effect of "Apply to all."

Incidentally, for internet protocols there is a separate Preference Pane you can download called More Internet.

By: blasdelf

blasdelf — Tue, 31 Jan 2006 20:10:21 -0800

RCDefaultApp is the only reliable way for a normal user to change these settings.

The Opens with... thing in the Finder's Get Info rarely works when you try to apply the setting to all files of that type.