Re: [gentoo-user] Re: Question about difference between emerge --update world and emerge vigra

[Daniel Pielmeier <daniel.pielmeier@googlemail.com>]

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James schrieb am 25.09.2008 20:32:
> Surely many folks would benefit from a formal, systematic approach
> to cleaning the world file?  I know every now and then, when a gentoo
> workstation gives me fits, I just emerge and unemerge things until
> it's happy (while multitasking too much). Often this leads to
> a polluted world file....... because I do not follow closely to
> the process details (distracted) during the repair-episode.
> 

Something in addition to this topic.

I asked on IRC (#gentoo-portage) if it is possible to show the reverse
dependencies of a package with portage. Zac Medico, one of the main
portage developers told me that it is possible with depclean.

emerge -pv --depclean <atom>

So I thought of writing a little script which calls this command for
every entry in the world file. As I have only limited programming skills
I wrote something quick in perl. It should be no problem to do it with a
shell script or something else too. It simply checks the output of
depclean for strings which only occur when the package has or has no
reverse dependencies. Then it prints the package to be checked and if it
is needed in world or not. It actually does not remove anything, so it
is up to you if you want to leave a package in world or not for whatever
reason you have.

The script could probably be improved in a few ways and it is slow as
depclean takes some time. It works for current stable portage. I don't
know if it will work for portage-2.2 as the output of depclean has
changed as far as I know.

Don't rely on this script to much. Because it works for me must not mean
it does for you. I have tested some cases and I worked every time until
now. So verify the output of a manual "emerge -pv --depclean <atom>" on
the "unneeded" entry first to be sure it is really not needed.

Regards,

Daniel


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#!/usr/bin/perl
#
#
#

use strict;
use diagnostics;
use warnings;

my ($package,$status,$line) = ();
my @depclean = ();
my $vdb_path = qx(portageq vdb_path);
chomp($vdb_path);

format STDOUT_TOP =
Atom:                                            Status: (required in world)
.

format STDOUT =
@<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< @<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
$package, $status
.

print "Examining: $vdb_path/world\n\n";

open(WORLD,"<$vdb_path/world") || die("world: $!");

foreach $package (<WORLD>) {
	chomp $package;
	@depclean = qx(emerge -pv --depclean "$package");
	foreach $line ( @depclean ) {
		if ( $line =~ ">>> These are the packages that would be unmerged:" ) {
			$status = "needed";
			write;
		} elsif ( $line =~ ">>> No packages selected for removal by depclean" ) {
			$status = "unneeded";
			write;
		} else {
			$status = "Error: Something bad happened";
		}
	}
}