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file tree to hash

by Anonymous Monk
on Apr 05, 2003 at 21:59 UTC ( #248343=perlquestion: print w/replies, xml ) Need Help??

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

I have a directory tree that is being provided in the form of a flat text file.

/root/dir1/file1
/root/dir1/file2
/root/dir1/file3
/root/dir2/file1


What I would like to do is create a hash out of this information. (note: this file could be of any length and have a variable directory depth)
hash{root}{dir1}{file1} = $value (where $value is determined at run time)

My initial thought was to split each line into an array, and then use the information in node_id=196317 to turn the array into the hash. But this seems less than optimal.

What would be the best way to handle this problem?

Replies are listed 'Best First'.
Re: file tree to hash
by dakkar (Hermit) on Apr 05, 2003 at 22:15 UTC
    #!/usr/bin/perl -w use Data::Dumper; {my $i=1; sub makevalue { return $i++; } } my $hash={};my $h0; my $l;my @c; while ($l=<DATA>) { $h0=$hash; @c=split '/',$l; for my $c (@c[0..$#c-1]) { next unless $c; $h0=($h0->{$c}||={}); } $h0->{$c[-1]}=makevalue($l); } print Dumper($hash); __DATA__ /root/dir1/file1 /root/dir1/file2 /root/dir1/file3 /root/dir2/file1

    Outputs:

    $VAR1 = { 'root' => { 'dir2' => { 'file1' => 4 }, 'dir1' => { 'file2' => 2, 'file3' => 3, 'file1' => 1 } } };

    What does it do: it splits each row, and walks down the HoH (creating empty hashes as needed), putting the computed values (in this example just a counter) on the leaf.

    I think this is more or less what you were describing, but I can't come up with a better solution.

    -- 
            dakkar - Mobilis in mobile
    
Re: file tree to hash
by pg (Canon) on Apr 06, 2003 at 00:09 UTC
    This is one way, less conventional:
    use strict; use Data::Dumper; my %hash; while (<DATA>) { chomp; s/\//}{/g; eval "\$hash".substr($_,1,length)."} = undef"; } print Dumper(\%hash); __DATA__ /root/dir1/file1 /root/dir1/file2 /root/dir1/file3 /root/dir2/file1
Re: file tree to hash
by chromatic (Archbishop) on Apr 05, 2003 at 22:09 UTC

    That's how I would do it. Why does it seem less than optimal? What do you mean by "best"?

Re: file tree to hash
by DrManhattan (Chaplain) on Apr 06, 2003 at 02:40 UTC

    Here's another eval() solution.

    #!/usr/bin/perl use strict; use Data::Dumper; my %hash; my $value = "determined at run time"; while (<DATA>) { chomp; eval '$hash{' . join( "}{", split(/\//) ) . "} = '$value'"; } print Dumper(\%hash); __DATA__ root/dir1/file1 root/dir1/file2 root/dir1/file3 root/dir2/file1
    Edit: merlyn is correct. Don't ever use this. A file named "root/dir1/file1}=1;`someprogram`;$hash{foo" could be used to execute an external program.

    -Matt

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