comment on

Hm, how about a hash per file and combine them on write?

use strict;
use warnings;

open FILE1, '<', 'file1.txt' or die ($!);
open FILE2, '<', 'file2.txt' or die ($!);

#- my %file1 = map { split '\|', $_ } <FILE1>;
my %file1 = map { chomp && s/\|$//g && split '\|', $_, 2 } <FILE1>;
#- my %file2 = map { split '\|', $_ } <FILE2>;
my %file2 = map { chomp && s/\|$//g && split '\|', $_, 2 } <FILE2>;
## we now have A1=>'dog' in one hash, and A1=>'Fido' in the other

close FILE1;
close FILE2;

open FILE3, '>', 'file3.txt' or die ($!);
for (sort keys %file1) {
   print FILE3 join('|',$_,$file1{$_},$file2{$_}),'|',"\n";
}
close FILE3;
[download]

untested

Simply put, create a hash "map" of each file, then find where the keys intersect and print out the result.

Caveats:

If there is no key in %file1, you won't get a result
If there is no key in %file2, you'll get a warning about printing an undefined value.
this makes assumptions about file formats
Update:Files that are not well-formed will cause problems -- for this and other reasons, there needs to be better error-checking.

None of those are unconquerable, but are some things to consider if you're taking the idea for production code. Update: modified the code based on thread below. Comments '#-' are old lines. A better thing to do than cheat with the file slurp might be something like:

my %file1;
while (<FILE1>) {
  chomp; s/\|[\s]*$//;
  my ($key, $val) = split '\|', $_, 2;
  $file1{$key} = $val;
}
[download]

Of course, that's not nearly as fun...

The Eightfold Path: 'use warnings;', 'use strict;', 'use diagnostics;', perltidy, CGI or CGI::Simple, try the CPAN first, big modules and small scripts, test first.

In reply to Re: combining 2 files with a comon field by radiantmatrix
in thread combining 2 files with a comon field by jjohhn

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