Re: Need help in comparing permissions/ownerships on different systems

Ayaz Ahmed Khan <ayaz@dev.slash.null>
Tue, 19 Dec 2006 21:21:14 +0500
"" typed:

[Follow-up set to comp.lang.perl.misc]

It results in a csv file contining perms on one system, then I could
use this to compare:


Not how to interpret "-rwx" fields. Thought of perl with expression
matching, or using the File:stat modules. Doesn't seem pratical.

   Any other ideas?

I once had a need to do something similar. I never completed the
application. The need either thined away into insignificance, or the
damage done wasn't so serious as had been presumed initially (the lead web
developer had accidentaly run `chmod -R 777 /` on one production system I
administrate). Nonetheless, the following snippet from the application
might help you. You might want to use a different module to traverse the
filesystem, as File::Glob doesn't quite work as I wanted it to.

sub read_filesystem
        my $startpath = shift;

        # Limitation: Doesn't do recursive globbing.
        use File::Glob ':glob';
        my @files = glob($startpath);

        use File::Stat::Ls qw(:all);

        foreach my $file (@files) {
                my @filestat = stat($file);

                my ($mode, $uid, $gid) = ($filestat[2], $filestat[4], $filestat[5]);

                my $file_obj = File::Stat::Ls->new;

                my $perm = $file_obj->format_mode($mode);
                my $octal = &convert_to_octal($perm);

                # Quick hack to workaround the fact that directory entries read from
                # MANIFEST have a trailing "/" character attached to them. Globbing
                # does not behave the same way with respect to directory entries.
                $file .= "/" if -d $file;
                $fs_live{$file} = [$uid, $gid, $perm, $octal];

### Given a string like "-rwx-r-xr-x", return equivalent octal representation.
sub convert_to_octal
        my $perm = shift;
        my $octal;

        my ($special, $user, $group, $other) = (0, 0, 0, 0);

        my ($x, $ur, $uw, $ux, $gr, $gw, $gx, $or, $ow, $ox) = split //, $perm;

        $user += 4 if $ur eq 'r';
        $user += 2 if $uw eq 'w';
        $user += 1 if $ux eq 'x';
        if ($ux eq 's') { $user += 1; $special += 4; }

        $group += 4 if $gr eq 'r';
        $group += 2 if $gw eq 'w';
        $group += 1 if $gx eq 'x';
        if ($gx eq 's') { $group += 1; $special += 2; }

        $other += 4 if $or eq 'r';
        $other += 2 if $ow eq 'w';
        $other += 1 if $ox eq 'x';
        if ($ox eq 't') { $other += 1; $special += 1; }

        $octal = $special . $user . $group . $other;

        return $octal;

I suggest reading through a few tutorials explaining Unix/Linux file modes
and permissions.

Ayaz Ahmed Khan

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