PATH=/usr/local/bin:/bin:/usr/bin considered harmful

[Sam Varshavchik <mrsam@xxxxxxxxxxxxxxx>]

The perl update that hit updates this week is causing a yum conflict with  
some locally-built packages, of this type:

Error: Package: courier-imap-4.10.0.20120202-2.17.x86_64 (installed)
          Requires: /bin/perl
          Removing: 4:perl-5.14.2-211.fc17.x86_64 (@anaconda-0)
              Not found
          Updated By: 4:perl-5.14.2-212.fc17.x86_64 (updates-released-local)
              Not found

> From what I can tell, the sequence of events is:

A) A local package's configure script executes "which perl", and puts that  
into each perl script's hashbang. So:

[root@octopus ~]# which perl
/bin/perl

This results in:

#! /bin/perl

B) The rpm package gets built. find-requires that puts this dependency into  
the package:

requires=/bin/perl

C) At install time, rpm seems to be smart to figure this out:

[root@octopus ~]# rpm -q --whatprovides /bin/perl
perl-5.14.2-211.fc17.x86_64

It's smart enough sees that thanks to the symlinks, /bin/perl=/usr/bin/perl.  
So the package gets installed, with these hashbangs.

D) A perl update hits:

[root@shorty x86_64]# rpm -q -l -p perl-5.14.2-212.fc17.x86_64.rpm | fgrep  
bin/perl
/usr/bin/perl
/usr/bin/perl5.14.2
/usr/bin/perlbug
/usr/bin/perlthanks

The new perl package contains /usr/bin/perl. At upgrade, dependency  
resolution is not smart enough to realize that the new package's  
/bin/perl=/usr/bin/perl, causing a conflict.

Having thought about it, I don't think it's unreasonable to do a "which  
$PROG", and stick it into the hashbang. I think that's a perfectly  
reasonable approach, with portability being the goal. The problem I see  
here, is that Fedora's bash is compiled with the default PATH placing a  
symlink, /bin, ahead of /usr/bin, in the PATH list:

[root@octopus ~]# strings /bin/bash | grep usr.bin
/usr/local/bin:/bin:/usr/bin

I think that bash needs to be recompiled, with the last two flipped, in the  
default shell PATH.

Until then, I need to hack each one of my locally-built package's rpm spec  
scripts, and manually prepend /usr/bin to the PATH. Which sucks.

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