Perl regex matches closest

Question

I am trying to match the last content with the final word.

For example, closest to a dog

"abcbdog"

Must be "bdog"

But instead I get "bcbdog"

How can I match only the last occurrence of "b" before "dog"

Here is my current regex:

/b.*?dog/si 

Thanks!

Answer 1

Regexes want to go from left to right, but you want to go from right to left to just cancel your line, change the pattern, and change the match:

 my $search_this = 'abcbdog'; my $item_name = 'dog'; my $find_closest = 'b'; my $pattern = reverse($item_name) . '.*?' . reverse($find_closest); my $reversed = reverse($search_this); $reversed =~ /$pattern/si; my $what_matched = reverse($&); print "$what_matched\n"; # prints bdog 

Answer 2

Try the following:

 /b[^b]*dog/si 

Match b , then everything that is not b (including nothing), and then dog .

Answer 3

TIMTOWTDI:

This method may even find multiple matches in a string, or it may be optimized if the start or end words are more common. Edit: Zero-width matches are now used to avoid deletion, and then the start and end lines are added.

 #!/usr/bin/env perl use strict; use warnings; use v5.10; #say my $string = 'abcbdog'; my $start = 'b'; my $end = 'dog'; my @found = grep { s/(?<=$end).*// } split( /(?=$start)/, $string ); say for @found; 

Answer 4

when you don’t already know what is the last character in front of the dog, it just works:

 my $str = 'abcbdog'; my @r = $str =~ /(.dog)/; print @r; 

prints bdog

Answer 5

The accepted answer seems a bit complicated if you are just trying to match the closest “b” to the “dog”, including the dog, you just need to make your matches before you look for greedy ones. For instance:

 # First example my $string1 = 'abcbdog'; if ( $string1 =~ /.+(b.*dog)/ ) { print $1; # Returns 'bdog' } # Second example, different string, same regex. my $string2 = 'abcbmoretextdog'; if ( $string2 =~ /.+(b.*dog)/ ) { print $1; # Returns 'bmoretextdog' } 

Or am I missing something? If you want to change the captured line according to what you want, just shift the brackets.

Answer 6

Try this code:

 ~/.* b.*?dog/si