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perl negating Regular Expression

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# 1  
Old 03-10-2009
Computer perl negating Regular Expression
hi all,

I have this particular piece of code

Code:
perl -pi -e 's#\&amp\;(\w\W*\w+\;)#\&$1#gm' filename.txt


the
Code:
(\w\W*\w+\;)

part should not contain an "&".

That means that if a string like &xxxxx&ecute; comes i wount be replacing the amp;.


thanks
Jathin
Last edited by Franklin52; 03-10-2009 at 07:33 AM.. Reason: adding code tags
# 2  
Old 03-10-2009
If I understand correctly:

Code:
(\w[^A-Za-z0-9_&]*\w+\;)

# 3  
Old 03-10-2009
i am a beginner in unix,

so just want to reconfirm what that code will do.

can you give a few line explanation.
# 4  
Old 03-10-2009
You said:

Quote:
the
Code:
(\w\W*\w+\)

part should not contain an "&".
As far as the regular expression above is concerned only the \W shorthand character class may contain the mentioned character. So, a possible solution is to use the extended class including the & character:

\W is short for [^\w]. \w is short for [A-Za-z0-9_]. So we end up with [^A-Za-z0-9_&].
# 5  
Old 03-10-2009
oh sorry.

I wanted to re iterate the requirement.

the present code is (\w\W*\w+\)

will remove the string "amp;" in the &xxxxx&ecute; even if the xxxxx is a part of \w* or \W*.

now the requirement is to change the code in such a way that if the xxxxx contains an &. the amp; must not be removed else the amp; must be removed.
# 6  
Old 03-10-2009
I cannot understand. I get this with your code:

Code:
% perl -pe 's#\&amp\;(\w\W*\w+\;)#\&$1#g' <<<'&amp;xxxxx&ecute;'
&amp;xxxxx&ecute;


Could you post a sample of your input file and an example of the desired output?
# 7  
Old 03-10-2009
the sample input

<p>A policy insight into the R&amp;D patent relationshi&amp;ecute;p</p>


expected output
<p>A policy insight into the R&amp;D patent relationshi&ecute;p</p>


but the present code generates

<p>A policy insight into the R&D patent relationshi&ecute;p</p>
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