[plt-scheme] Why .dmg for Mac source distributions?

From: Jakub Piotr Cłapa (jpc-ml at zenburn.net)
Date: Thu Sep 10 09:48:51 EDT 2009

On 09-09-10 12:23, Noel Welsh wrote:
> On Thu, Sep 10, 2009 at 6:41 AM, Peter Michaux<petermichaux at gmail.com>  wrote:
>> I have downloaded and installed MzScheme from the Mac source code
>> distribution. It really struck me as uncommon that a source is
>> distributed in a dmg file. I've been using OS X and installing various
>> software for quite a while and haven't encountered a dmg being used
>> for this purpose before. A tarball is usual and the same tarball is
>> used for *NIX.
> I find different people use OS X in very different ways. I use it like
> a Unix box w/ Emacs, tarballs etc. Some of my friends use little GUI
> apps when perfectly acceptable CLI apps exist, under powered text
> editors like Smultron etc. Clearly they have weak minds. I expect
> they'd prefer a disk image over a tarball. You can always download the
> Unix src tarball if you want.

I guess that the main advantage of dmgs is that they can hold any 
metadata OS X can handle (including resource forks and more conventional 
xattrs). This way someone won't break anything by using some old tar 
program for unpacking (most UNIX tools before 10.4 did not support any 
xattrs and resource forks; even cp). This problems are not very 
important for source code.

On the other hand the default configuration of Safari automatically 
"unpacks" dmg images just like tar.gz (leaving you with a folder in 

PS. Using
open something.tar.gz
in the Terminal has an advantage that it automatically handles the 
one-dir-with-files vs. many-loose-files problem. (it also works for 
7-zip, tar.lzma and rar files if you have The Unarchiver installed)

Jakub Piotr Cłapa

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