[lug] parsing between two lists

[qqq1one @yahoo.com]

I'm not much of a perl composer (yet).  Could you check my
understanding of how this script works?

The first while loop builds an internal list of everything that is in
file_a.txt.  Then the second while loop deletes everything from the
list if it is also found in file_b.txt, no?

Getting this script to list everything in file_b.txt that is not in
file_a.txt can be accomplished just by swapping the file names.

But how would you get it to list everything that is common to both
files?  Can you just add some sort of "NOT" to the second while loop to
accomplish this?

--- Rob Nagler <nagler at bivio.biz> wrote:
> > ...but I would rather have a list that shows what's in fileA that's
> not
> > in fileB:
> 
> I just had this problem yesterday.  Here is a very quick hack:
> 
> #!/usr/bin/perl -w
> my($FILE_A) = {};
> open(IN, 'file_a.txt') || die("open 'file_a.txt': $!");
> while (<IN>) {
>     chomp;
>     next unless $_;
>     $FILE_A->{lc($_)}++;
> }
> close(IN) || die;
> 
> open(IN, 'file_b.txt') || die("open 'file_b.txt': $!");
> while (<IN>) {
>     chomp;
>     next unless $_;
>     delete($FILE_A->{lc($_)});
> }
> print join("
", sort(keys(%$FILE_A))), "
";
> 
> 
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