Using hash to parse a Flat File

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

Dear Monks,

I created a hash array out of my first file (File 1) and wrote the cod
+e like this:- 

File 1 looks like this:-
John        10
Mathew        16
Andrew        27

#!/usr/bin/perl -w

use strict;
use warnings;

      my %href;
      my $fn = <>;
      open(FH, "$fn") || die "Cannot open file";

      while (<FH>) {
              chomp($_);
              $href{$1} = $2 if $_ =~ /(\S+)\s+(\S+)/;
      }

      while (my ($key, $value) = each(%href)) {
              print $key. ", ". $value."\n";
      }


       Okkkk. Now I have a 1.2 GB file thats I need to parse and print
+ my results based on my hash values and keys. File 2 Looks like this 
+:-

File 2:-
>John
40 34 40 40 40 40 17 40 40 35 40 40 40 40 40 40 40 20 40 40 40 30 40 4
+0 40 40 40
 40 37 40 40 40 40 40 25 40
>Mathew
40 40 44 40 40 40 40 50 40 40 40 40 50 40 40 40 40 40 6 40 40 45 40 40
+ 40 40 40 
40 40 40 29 40 40 40 6 40
>Andrew
40 40 40 40 39 40 40 40 40 40 40 40 35 40 40 40 40 40 40 40 40 27 40 4
+0 40 40 40
 40 33 40 40 40 40 4 40 40

     ----------------------- END --------------------

     Now what I need to do is suppose John in File 1 has value 10. So 
+in File 2 if only John record at the position 10 has the value >= 20 
+I need to take it right and print it. 

Since John Record at 10th position = 35 which is greater than 20 so I 
+have to print my  result as:-

Result File:-
John 10 35.

   Thanks
[download]

Comment on Using hash to parse a Flat File Download Code

Replies are listed 'Best First'.
Re: Using hash to parse a Flat File by kyle (Abbot) on Oct 20, 2008 at 17:05 UTC
If your names always have a > before them, you could set $/ to that to pick out the records. It might look something like this: `$/ = '>'; while ( <> ) { chomp; next if ! s{ \A (\S+) \s+ (?= \d ) }{}xms; my $name = $1; my @numbers = split /\D+/; my $one_number = $numbers[$href{$name} - 1]; if ( $one_number >= 20 ) { print "$name $href{$name} $one_number\n"; } }` [download] The above code is not tested, but it should be a good start. By the way, `%href` is not a very good name for a hash. It's only a little better if it's the name of a hash reference, or maybe if you're storing URLs. Also by the way, it's better to use <code> tags only for your code and not for the whole article.	[reply] [d/l] [select]
Re: Using hash to parse a Flat File by apl (Monsignor) on Oct 20, 2008 at 18:27 UTC
You might want to modify the die in `open(FH, "$fn") \|\| die "Cannot open file";` to contain $fn and $! (the returned error-code). At some point, you'll be grateful.	[reply] [d/l]