Re: CFT: new BSD-licensed sort available

From: Jonathan Anderson <jonathan.anderson_at_cl.cam.ac.uk>
Date: Wed, 14 Mar 2012 22:14:28 +0000
On 14 Mar 2012, at 21:10, Adrian Chadd wrote:
> Hi,
> 
> This makes me think of the whole debian-y way of replacing the mailer
> programs using some magic alias program.
> 
> So you could intall gnusort, bsdsort, and then some config file would
> determine which was used.
> 
> 'sort' would then be a symlink to said magic program, that'd look at
> its argv[0], look at the contents of that file, and exec() the right
> one.

In fact, the runtime behaviour of the Debian "alternatives" system is simpler than that:
http://segfault.in/2010/04/using-the-debian-alternatives-system/

The custom Perl script with a config file is used to set up symlinks, which at runtime are... well, just symlinks. For instance, /usr/bin/vim is a symlink to /etc/alternatives/vim, which is itself a symlink to a binary like vim.gtk (example shamelessly stolen from the linked page, since I no longer have any Debian boxes to check for myself on :). No magic binaries or argv[0] fu.

In one way, it's an elegant solution. On the other, it's a classic example of Wheeler's Law in action. :)


Jon
--
Jonathan Anderson

Research Student, Security Group
Computer Laboratory
University of Cambridge

+44 (1223) 763747
jonathan.anderson_at_cl.cam.ac.uk
Received on Thu Mar 15 2012 - 00:04:03 UTC

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