Re: extract line

Welcome to the monastery.

This code does what you describe as being wanted:

$ perl -Mstrict -Mwarnings -e '
    use autodie;
    use Tie::File;

    my $re = qr{^((\d+).+$)}s;

    my %data_for_part;

    open my $f1, "<", "pm_1045452_file1.txt";
    while (<$f1>) {
        /$re/;
        $data_for_part{$2} = $1;
    }
    close $f1;

    tie my @file2, "Tie::File", "pm_1045452_file2.txt";
    print $data_for_part{$_} for @file2;
    untie @file2;
'
3478749:AA:1D:AAA:DescriptionsY:C:2
3633731:AA:3E:AAA:DescriptionsZ:C:2
[download]

I made a minor change to "File1" to show different Descriptions:

$ cat pm_1045452_file1.txt
3478748:AA:1D:AAA:DescriptionsX:C:2
3478749:AA:1D:AAA:DescriptionsY:C:2
3633731:AA:3E:AAA:DescriptionsZ:C:2
[download]

"File2" data is as you show it:

$ cat pm_1045452_file2.txt
3478749
3633731
[download]

Notes:

You don't need to chomp any input nor add any newlines to the output.
There's no temporary arrays to process.
Tie::File comes standard with Perl: you won't need to install it.

"This file has over a million lines and is running very slow."

Given that you've been provided with a number of solutions, use Benchmark to determine which works best for you. (That module also comes standard with Perl.)

[Aside: The code you posted is difficult to read due to the <code> tag issue. You appear to have made an effort but were unsuccessful: see Writeup Formatting Tips for how, where and why to do it.]

-- Ken

Comment on Re: extract line Select or Download Code

Replies are listed 'Best First'.
Re^2: extract line by lallison (Novice) on Jul 21, 2013 at 17:46 UTC
what should $2 refer to?	[reply]
Re^3: extract line by kcott (Archbishop) on Jul 22, 2013 at 09:09 UTC
`$1`, `$2` (and `$3`, ..., etc.) hold the data that has been captured by a regular expression. This is fairly basic stuff, so perhaps a read of the perlretut - Perl regular expressions tutorial would be useful; it's section "Extracting matches" has a better, and more detailed, description than my one sentence. -- Ken	[reply] [d/l] [select]
Re^2: extract line by lallison (Novice) on Jul 21, 2013 at 17:28 UTC
are you running the file with cat pm_1045452_file2.txt statement?	[reply]
Re^3: extract line by kcott (Archbishop) on Jul 22, 2013 at 08:50 UTC
If you're unfamiliar with nix OSes, perhaps what I posted requires a little further explanation: The actual code I ran is the "`perl -Mstrict -Mwarnings -e ' ... '`"* part (see perlrun). The two lines immediately following that second single quote is the output produced by the print statement. `cat` is a commonly used nix command (unrelated to Perl) that prints the contents of file(s). You can read "`$ cat pm_1045452_file1.txt`"* as "Here's the contents of the file `pm_1045452_file1.txt`:". This is entirely unrelated to the Perl code; it merely shows the data the Perl code is using (which, as stated, I had slightly modified). [In case you didn't know, "nix" is just an umbrella term for any UNIX-like OS.]* -- Ken	[reply] [d/l] [select]