extract substring between token a and token b

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

hi

i'm trying to extract $substring from $text - where $text is a block of html and $substring is anything between

 and


in $text.

i've tried

$text =~ /%<\!--begin-->%(.*?)%<\!--end-->/;
$substring = $1;
print $substring;

but this doesn't seem to be working. i'm not sure if my regex is right first of all. also, is there any way to do this without using the global variable $1?

thanks

Comment on extract substring between token a and token b

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Re: extract substring between token a and token b by LassiLantar (Monk) on Jul 29, 2004 at 01:47 UTC
This works... I'm not sure what the "%"s in your regex were for. `#!/usr/bin/perl $text = "<!--begin-->this is a line of text<!--end--><!--begin-->anoth +er one<!--end-->"; @lines = $text =~ /<\!--begin-->(.*?)<\!--end-->/g; foreach (@lines) { print $_ . "\n"; }` [download] Peace! LassiLantar	[reply] [d/l]
Re: extract substring between token a and token b by itub (Priest) on Jul 29, 2004 at 00:51 UTC
If the string you want to match spans more than one line, you need to use the /s modifier, because otherwise the dot doesn't match the newline character. If you do the pattern matching in list context with the /g (global) option, you can capture all the matches in one array without using $1. e.g., `@matches = $text =~ /(pattern)/g;`	[reply] [d/l]
Re: extract substring between token a and token b by philosophia (Sexton) on Jul 29, 2004 at 03:17 UTC
you guys are awesome thanks	[reply]
Re: extract substring between token a and token b by revdiablo (Prior) on Jul 29, 2004 at 17:02 UTC
Your question has been directly answered, but there is a major pitfall to your approach. Even using the non-greedy match, you will run into problems with nested tags. Example: `$input = '<foo>bar<foo>oops</foo></foo>'; print $input =~ m{<foo>(.*?)</foo>}, "\n"; __OUTPUT__ bar<foo>oops` [download] This is one big reason you should avoid simple regular expressions for parsing nested formats, like HTML. The best solution is to use a real parser that actually understands its source data, rather than simple pattern matches.	[reply] [d/l]