Perl Regex匹配磁铁链路的Infohash

Question

即时尝试使用Perls Regex从Torrent Magnet链接中提取信息哈希 磁铁链接看起来像：

磁体：

但有时它可以看起来像：
磁铁：？XT= URN：BTIH：8AC3731AD4B039C05393B5404AFA6E7397810B41

试图提取的部分是8AC3731AD4B039C05393B5404AFA6E7397810B41

我试图捕捉到第一个'＆'的一切，或者如果它只包括infohash然后达到行的结尾，我试过了一对夫妇，但不能让它正常工作

我在下面只捕获第一个字符

if ($tmpVar =~ m/magnet\:\?xt=urn\:btih\:([[:alnum:]]+?)/i) {
  $mainRes{'hash'} = $1;
}

.

我也尝试了捕获后添加＆| $，但它只是出现错误
谢谢

Answer 1

You could use:

/\burn:btih:([A-F\d]+)\b/i

Or if the hash is always 40 chars:

/\burn:btih:([A-F\d]{40})\b/i

Answer 2

As you've already discovered, you don't want to use the ? in your regular-expressions. Here's why:

The ? in pattern+? makes your regex "non-greedy", meaning it will try to use as few characters as possible while still matching the pattern you specify. So

"8AC3731AD4B039C05393B5404AFA6E7397810B41" =~ /(\w+?)/

just returns "8" while

"8AC3731AD4B039C05393B5404AFA6E7397810B41" =~ /(\w+)/

returns the whole string.

if ($tmpVar =~ m/magnet:\?xt=urn:btih:([[:alnum:]]+)/i) {
    $mainRes{'hash'} = $1;
}

Answer 3

This is why the gods of CPAN gave us URI, to parse out parts of URIs, which you can then parse with a regex.

#!/usr/bin/perl
use URI;
use URI::QueryParam;
use Data::Dumper;

my $u = URI->new( shift() );
my $xt = $u->query_form_hash->{xt};

my ($hash) = $xt =~ m{^urn:btih:(.*)$};
print "$hash\n";

Presuming your magnet URI on the command line.