CODEWITHSUNDEEP
perl
Sandra Schlichting
Sandra Schlichting

Reputation: 25986

Why wrong output from the RegEx?

When I run the script below, I get

$VAR1 = [
          'ok0.ok]][[file:ok1.ok',
          undef,
          undef,
          'ok2.ok|dgdfg]][[file:ok3.ok',
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef
        ];

where I was hoping for ok0.ok ok1.ok ok2.ok ok3.ok and ideally also ok4.ok ok5.ok ok6.ok ok7.ok

Question

Can anyone see what I am doing wrong?

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my $html = "sdfgdfg[[file:ok0.ok]][[file:ok1.ok ]] [[file:ok2.ok|dgdfg]][[file:ok3.ok |dfgdfgg]] [[media:ok4.ok]] [[media:ok5.ok ]] [[media:ok6.ok|dgdfg]] [[media:ok7.ok |dfgdfgg]]ggg";

my @seen = ($html =~ /file:(.*?) |\||\]/g);

print Dumper \@seen;

Upvotes: 2

Views: 124

Answers (6)

rubber boots
rubber boots

Reputation: 15184

this is what your regex does:

 ...
 my $ss = qr {
              file: # start with file + column as anchor
              (         # start capture group
               .*?      # use any character in a non-greedy sweep
              )         # end capture group
              \s        # end non-greedy search on a **white space**

              |     # OR expression encountered up to here with:
              \|     # => | charachter  
              |      # OR expression encountered up to here with:
              \]       # => ] charachter  
              }x;

 my @seen = $html =~ /$ss/g;
 ...

and this is what your regex is supposed to do:

 ...
 my $rb = qr {
             \w :      # alphanumeric + column as front anchor
             (         # start capture group 
              [^]| ]+  # the terminating sequence
             )         # end capture group 
            }x;

 my @seen = $html =~ /$rb/g;
 ...

If you want a short, concise regex and know what you do, you could drop the capturing group altogether and use full capture chunk in list context together with positive lookbehind:

 ...
 my @seen = $html =~ /(?<=(?:.file|media):)[^] |]+/g; # no cature group ()
 ...

or, if no other structure in your data as shown is to be dealt with, use the : as only anchor:

 ...
 my @seen = $html =~ /(?<=:)[^] |]+/g;   # no capture group and short
 ...

Regards

rbo

Upvotes: 1

Kiran Chaudhary
Kiran Chaudhary

Reputation: 144

I hope this is what you required.

#!/usr/bin/perl

use strict;  

use warnings;

use Data::Dumper;


my $string = "sdfgdfg[[file:ok0.ok]][[file:ok1.ok ]] [[file:ok2.ok|dgdfg]][[file:ok3.ok |dfgdfgg]] [[media:ok4.ok]] [[media:ok5.ok ]] [[media:ok6.ok|dgdfg]] [[media:ok7.ok |dfgdfgg]]ggg";

my @matches;

@matches = $string =~ m/ok\d\.ok/g;

print Dumper @matches;

Output:

$VAR1 = 'ok0.ok';

$VAR2 = 'ok1.ok';

$VAR3 = 'ok2.ok';

$VAR4 = 'ok3.ok';

$VAR5 = 'ok4.ok';

$VAR6 = 'ok5.ok';

$VAR7 = 'ok6.ok';

$VAR8 = 'ok7.ok';

Regards, Kiran.

Upvotes: 0

Konerak
Konerak

Reputation: 39763

It looks like you are trying to match everything starting with file: and ending with either a space, a pipe or a closing square bracket.

Your OR-statement at the end of the regexp needs to be between (square) brackets itself though:

my @seen = ($html =~ /file:(.*?)[] |]/g);

If you want the media: blocks as well, OR the file part. You might want a non-capturing group here:

my @seen = ($html =~ /(?:file|media):(.*?)[] |]/g);

How it works

The first statement will capture everything between 'file:' and a ], | or .

The second statement does the same, but with both file and media. We use a non-capturing group (?:group) instead of (group) so the word is not put into your @seen.

Upvotes: 1

Borodin
Borodin

Reputation: 126722

Depending on the possible characters in the file name, I think you probably want

my @seen = $html =~ /(?:file|media):([\w.]+)/g;

which captures all of ok0.ok through to ok7.ok.

It relies on the file names containing alphanumeric characters plus underscore and dot.

Upvotes: 0

DavidO
DavidO

Reputation: 13942

A negated character class can simplify things a bit, I think. Be explicit as to your anchors (file:, or media:), and explicit as to what terminates the sequence (a space, pipe, or closing bracket). Then capture.

my @seen = $html =~ m{(?:file|media):([^\|\s\]]+)}g;

Explained:

my @seen = $html =~ m{
    (?:file|media):        # Match either 'file' or 'media', don't capture, ':'
    ( [^\|\s\]]+ )         # Match and capture one or more, anything except |\s]
}gx;

Capturing stops as soon as ], |, or \s is encountered.

Upvotes: 2

Martin
Martin

Reputation: 12203

Try with 

my @seen = ($html =~ /\[\[\w+:(\w+\.\w+)\]\]/g);

Upvotes: 1

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