regexps and hashes

base_16 has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to parse some cddb files that i have laying around with perl, but unfortunately, the script i wrote only picks up every other line. Why is this?

#!/usr/bin/perl -w
##base16's cddb script

%title=();
sysopen(FILEDATA, "$ARGV[0]", O_RDWR) or die "no input";
flock(FILEDATA, 2);

while (<FILEDATA>)
{
$match = <FILEDATA>;
if ($match =~ /^TTITLE(\d+)=(.+)$/) { $title{$1} = $2; }
}

while ( ($key, $value) = each %title) {
    print $key, '-', $value, "\n";
}
close(FILEDATA);
[download]

Comment on regexps and hashes Download Code

Replies are listed 'Best First'.
RE: regexps and hashes by lhoward (Vicar) on May 15, 2000 at 21:44 UTC
Your problem is with this piece of code.... `while (<FILEDATA>) { $match = <FILEDATA>; if ($match =~ /^TTITLE(\d+)=(.+)$/) { $title{$1} = $2; } }` [download] change it to `while (<FILEDATA>) { $match = $_; if ($match =~ /^TTITLE(\d+)=(.+)$/) { $title{$1} = $2; } }` [download] and it should work properly. Your 2 calls to <FILEDATA> are causing 2 reads to happen, making it skip every other line (as you discovered).	[reply] [d/l] [select]
RE: RE: regexps and hashes by Vane (Novice) on May 15, 2000 at 22:35 UTC
or simply `while (<FILEDATA>){ if (/^TTITLE(\d+)=(.+)$/) { $title{$1} = $2; } }` [download]	[reply] [d/l]
RE: RE: regexps and hashes by base_16 (Beadle) on May 15, 2000 at 21:47 UTC
Sweet! thanks. This is why i love perlmonks.org....	[reply]
RE: regexps and hashes by turnstep (Parson) on May 16, 2000 at 19:15 UTC
Also note that since you put everything into a hash and then extract it, the order your script outputs will most likely NOT be the same as the order in the original file. Try something like this to smooth things out: `while (<FILEDATA>) { /$TTITLE(\d+)=(.+)$/ and print "$1-$2\n"; }` [download] or if you need to save them for later use: `while (<FILEDATA>) { /$TTITLE(\d+)=(.+)$/ and push(@titles, "$1=$2\n"); } ## Then just: print @titles;` [download] These ways also allow more than one TTITLE of the same number to exist, if that's a factor. A hash will only save the value of the last one read.	[reply] [d/l] [select]