Replacing substrings with links

ovedpo15 has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks!
I have the following hash ref:

{
  '/a/b/c/dt/data/SUSE/tool/0.9.0' => '/a/b/c/dt/tools/SUSE/tool/0.9.0
+',
  '/nfs/us/tools/SUSE12' => '/usr/bin',
  '/a/b/c' => '/p'
};
[download]

Each key is a path, which is the absolute path of the value. For example:

realpath /p # Yields /a/b/c
[download]

For each value, I would like to replace the substring with the other link, if such exists. In our case, we have '/a/b/c/dt/sde/tools/em64t_SUSE/tool/0.9.0' and '/a/b/c' => '/p', so I would like to have:

{
  '/a/b/c/dt/data/SUSE/tool/0.9.0' => '/p/dt/tools/SUSE/tool/0.9.0',
  '/nfs/us/tools/SUSE12' => '/usr/bin',
  '/a/b/c' => '/p'
};
[download]

I thought about doing the following - do two foreach loops on the keys (one nested inside the other). In the second loop, I would ignore the case where the two keys are the same. Then I would compare the values (if it starts with the value, then replace it). The current code that I code:

foreach my $actual_path_to_check (keys(%{$virtual_paths_href})) {
    foreach my $current_actual_path (keys(%{$virtual_paths_href})) {
        next if ($actual_path_to_check eq $current_actual_path);
        if ($virtual_paths_href->{$current_actual_path} =~ /^$virtual_
+paths_href->{$actual_path_to_check}/) {
            # Replace
        }
    }
}
[download]

But then I figured that I don't know how many loops I would need. For example, if I have a case of a link which points to another link (like /x -> /y -> /z). In that case, I would need another loop over the values. The goal is to replace the substrings parts with the other links of other keys (not depending of the environment). How it can be done?

Comment on Replacing substrings with links Select or Download Code

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Re: Replacing substrings with links by LanX (Saint) on Feb 05, 2022 at 22:10 UTC
> Each key is a path, which is the absolute path of the value. For example: > realpath `/p` # Yields `/a/b/c` > For each value, I would like to replace the substring with the other link, if such exists. In our case, we have `"/a/b/c/dt/sde/tools/em64t_SUSE/tool/0.9.0"` and `"/a/b/c" => "/p"` , so I would like to have: You are aware that a file system can have multiple links pointing to the same "realpath", right? And if you had multiple links qualifying like an additional `"/a/b" => "/q"` you'd probably want to replace `"/a/b/c"` first to have a shorter result. This will become pretty messy without further clarification. Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re: Replacing substrings with links by LanX (Saint) on Feb 05, 2022 at 20:30 UTC
This does a part of the job except > I would ignore the case where the two keys are the same. ... because I doubt this will lead to any predictable results anyway (sorting matters). `use strict; use warnings; use Data::Dump qw/pp dd/; my $h_orig = { '/a/b/c/dt/data/SUSE/tool/0.9.0' => '/a/b/c/dt/tools/SUSE/tool/0.9.0 +', '/nfs/us/tools/SUSE12' => '/usr/bin', '/a/b/c' => '/p' }; my $pattern = join "\|", map quotemeta, keys %$h_orig; my %copy = %$h_orig; s/^($pattern)/$h_orig->{$1}/g for values %copy; pp $h_orig, \%copy;` [download] `-- mode: compilation; default-directory: "d:/tmp/pm/" -- Compilation started at Sat Feb 5 21:29:56 C:/Strawberry/perl/bin\perl.exe -w d:/tmp/pm/replace_patl.pl ( { "/a/b/c" => "/p", "/a/b/c/dt/data/SUSE/tool/0.9.0" => "/a/b/c/dt/tools/SUSE/tool/0.9 +.0", "/nfs/us/tools/SUSE12" => "/usr/bin", }, { "/a/b/c" => "/p", "/a/b/c/dt/data/SUSE/tool/0.9.0" => "/p/dt/tools/SUSE/tool/0.9.0", "/nfs/us/tools/SUSE12" => "/usr/bin", }, ) Compilation finished at Sat Feb 5 21:29:57` [download] Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^2: Replacing substrings with links by choroba (Cardinal) on Feb 05, 2022 at 20:40 UTC
If more than one iteration is needed, you can use a loop with a "change" flag: `my $change = 1; while ($change) { $change = 0; $change \|\|= s/^($pattern)/$h_orig->{$1}/g for values %copy; }` [download] `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l] [select]
Re^3: Replacing substrings with links by LanX (Saint) on Feb 06, 2022 at 14:59 UTC
I think it's easier and more efficient to switch the loops. `for (values %copy) { 1 while # repeat till no replacement +left s/^($pattern)/$h_orig->{$1}/g; }` [download] But I have trouble to come up with a test case covering the complicated implications. ( Update Anyone? ) `use strict; use warnings; use Data::Dump qw/pp dd/; my $h_orig = { '/a/b/c/dt/data/SUSE/tool/0.9.0' => '/a/b/c/dt/tools/SUSE/tool/0.9.0 +', '/nfs/us' => '/usr/bin', '/a/b/c' => '/nfs/us' }; my $pattern = join "\|", map quotemeta, keys %$h_orig; my %copy = %$h_orig; for (values %copy) { 1 while s/^($pattern)/$h_orig->{$1}/g; } pp $h_orig, \%copy;` [download] `-- mode: compilation; default-directory: "d:/tmp/pm/" -- Compilation started at Sun Feb 6 15:59:06 C:/Strawberry/perl/bin\perl.exe -w d:/tmp/pm/replace_pat2.pl ( { "/a/b/c" => "/nfs/us", "/a/b/c/dt/data/SUSE/tool/0.9.0" => "/a/b/c/dt/tools/SUSE/tool/0.9 +.0", "/nfs/us" => "/usr/bin", }, { "/a/b/c" => "/usr/bin", "/a/b/c/dt/data/SUSE/tool/0.9.0" => "/usr/bin/dt/tools/SUSE/tool/0 +.9.0", "/nfs/us" => "/usr/bin", }, ) Compilation finished at Sun Feb 6 15:59:06` [download] Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^4: Replacing substrings with links by choroba (Cardinal) on Feb 06, 2022 at 17:20 UTC
Re^5: Replacing substrings with links (updated) by LanX (Saint) on Feb 06, 2022 at 17:23 UTC
Re^3: Replacing substrings with links by LanX (Saint) on Feb 05, 2022 at 20:46 UTC
I really have a problem with the whole fuzzy concept, otherwise I would try to work with sorting first. Now apparently there are values which include their own key, otherwise this exclusion criteria wouldn't be needed. But what kind of sane link is self referential? Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply]