Application has to be transferred in a .sit

Hi, I've been trying to figure out how applications work in OS X and I can't find any information. I don't just mean how to run them or move them; I know applications in a Mac can be run from anywhere and most are just one file.

My question is how does OS X know it's an application. I use a few Macs at work and I had a .sit file with an application in it. I extracted the application and installed it on one computer (it's an application with an installer). Then I transferred the installer to another Mac and it didn't realize the file was an application and asked me how to open it.
I finally found out I had to keep it in the .sit when transferring and then extract it there, or other Macs wouldn't have any idea it was an application. Could anyone tell me how applications work on a Mac and why they have to be transferred while in an archive? Thanks a lot for your help.

A Macintosh application can only exist on a Mac-formatted disk. If you try to copy a Mac app to a disk with a Windows format (FAT32) then the file will lose the metadata needed to recognize it as a Mac application. Same thing if it is sent as an eMail attachment or sent over FTP.

To preserve the metadata, you can enclose a Mac app in a disk image (.dmg) or a Stuffit archive (.sit) before copying.

Depends what version of the Mac OS the file is for, old Mac programs used to be composed of two parts, a resource and data fork. If either got messed up, so did the file, and going from mac -> fat32 -> mac is just the way to mess it up, so keep it compressed as suggested.

OS X programs are in packages (.app), if you go into the terminal you will actually find that the Mail.app program is actually a directory (you can do a cd mail.app) and then you can access all the elements that make the application package.

You can also do this from Finder, right clicking and selecting the option from the popup menu item "Show Package Contents".

These types of applications are in fact easier to transport over different file systems than the old classic OS files.

However most of the error occurs from the translation from Mac HFS/HFS+ disk format which uses those data and resource forks I was on about.

Vicky

Wow, thanks a lot. That's exactly what I what I was trying to find out. I'm going to get a Mac at home soon too, so I'm glad to get a better feel for how things like this work. Thanks again!

lil said:

OS X programs are in packages (.app), if you go into the terminal you will actually find that the Mail.app program is actually a directory (you can do a cd mail.app) and then you can access all the elements that make the application package.

Click to expand...

Take a package off of a Mac (HFS/HFS+) disk, and it looses the bundle bit (part of the HFS metadata) and becomes as dead as any old-style with a resource fork.