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

Oh wise ones... I have the need to parse a file that lists variables. The file format is something like *rvd*daemonPort : 7500 or hostname*rvd*daemonPort : 7500 or could even extend to hostname*rvd*RTD*daemonPort : 7500. So the variables are scoped either globally or locally. Also, the variables will be unknown to me until I parse the file. So, Parsing the file is not difficult. The issue for me is putting the data into a usable array or hash. 
        while( <FILE> ) {

                @tmp = split(/\*/);

            SWITCH: {
                for ($i = 0; $i <= $#tmp; $i++) {
                  if ($tmp[$i]) {
                    # make sure the first value is the key.
                    print "Setting key : $KEY\n", if ($Verbose);
                    $KEY = "$tmp[$i]";
                        # populate the key with the other values
                        # hostname*rvd*daemonPort : 7500
                        for ($i; $i <= $#tmp; $i++) {
                                # reached the last var populate the va
+lue
                                if ( $tmp[$i] =~ /^(\w+)\s+\:\s+([A-Z.
+0-9_\/])/ig) {

                                  $Vars{$KEY}{$tmp[$i - 1]}{$1} => $2;

                                  print "$tmp[$i]";
                                }else{
                                  $Vars{$KEY}{$tmp[$i]};
                                }
                        }
                    last SWITCH;
                  }
                }
            }

        }   # while <file>

[download]
Obviously this is not going to work correctly. The real problem is getting a hash that looks like this $hash{rvd}{RTD}{daemonPort} => 7500; without knowing how deep I am going to go. Any ideas out there?

Replies are listed 'Best First'.
Re: Parse file to Hash of Hash etc.
by mrborisguy (Hermit) on May 18, 2005 at 18:08 UTC
    This code should make a string that looks like $hash{'hostname'}{'rvd'}{'RTD'}{'daemonPort'} = 7500, and then run an eval on it. 
    my %hash;
while( <> ) {
    my ( $front, $back ) = split /\s*:\s*/;
    my @keys = split /\*/, $front;
    eval( '$hash' . ( join '', map { "{'$_'}" } @keys ) . "=" . $back 
+);
}

    [download]
    Warning: Untested code.

    You could also do probably more easily do this with a recursive sub.
[reply]
[d/l]
[select]
[reply]
        Point taken. And a good read too. Thanks! I'll try to be more careful next time. Do you have a suggestion of the simplest way to do this safely?
[reply]
        I think I understand what you are saying but the code from mrborisguy works great for me and I understand what it is doing, which for me is very important. I do not like to just cut and past code because in the end someone has to support it. I did try the data dumper but am unable to access the data on the return. ?? Probably since I don't know what I am doing :) maybe a plus one for for mrborisguy ?
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      VERY cool One question.... What is recursive sub? I can not find it in my perl book.
[reply]
        A recursive sub is when a sub calls itself in some form.
        The best example of this usually given is the mathematical function factorial (denoted by !). Are you familiar with it? 4! = 4*3*2*1. 7! = 7*6*5*4*3*2*1. In general, n! = n*(n-1)*(n-2)*...*2*1. But you could also say that n! = n*(n-1)!.

        so if you would make a sub called factorial, then it would be something like this: 
        sub factorial {
     my $n = shift;
     return $n * &factorial( $n - 1 );
}

        [download]
        but this obviously doesn't work, 'cause it will keep going and going, so you need a stopping point too. 
        sub factorial {
     my $n = shift;
     if ( $n == 1 ) { return 1 }
     return $n * &factorial( $n - 1 );
}

        [download]
        Try searching Google for recursive functions, recursive subs, recursion, etc.
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[d/l]
[select]
      The untested code works just fine for me.
[reply]

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