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moata_u
Asked: 2011-03-07 04:19:22 +0800 CST

Problem manipulating text using grep

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I want to search for a line that contains log4j and take 7 lines before and 3 lines after the match.

grep -B7 -A3 "log4j" web.xml

After that I want to add comment tags before this paragraph and after it.

<!--
paragraph that i found by grep
-->

I wrote this script bellow:

search=`find . -name 'web.xml'`
text=`grep -B7 -A3 "log4j" $search`
sed -i "/$text/c $newparagraph" $search

It's not working. Is there any way to just add comment symbol not replace the paragraph?

What I want to the script to do:

  1. search for the paragraph
  2. append
  3. append --> at the end

Edit: This is the paragraph that am trying manipulate :

<context-param>
    <param-name>log4jConfigLocation</param-name>
    <param-value>/WEB-INF/classes/log4j.properties</param-value>
</context-param>

<listener>
    <listenerclass>
        org.springframework.web.util.Log4jConfigListener
    </listener-class>
</listener>

This paragraph is part of many paragraphs! I want make it like this:

<!--
<context-param>
    <param-name>log4jConfigLocation</param-name>
    <param-value>/WEB-INF/classes/log4j.properties</param-value>
</context-param>

<listener>
    <listenerclass>
        org.springframework.web.util.Log4jConfigListener
    </listener-class>
</listener>
-->
bash

1 Answers

  1. Best Answer

    This would be better done with an XML library, but here it is in sed...

    Sed has i and a commands for inserting and appending lines. I think the following script will help.

    sed -n '/log4jConfigLocation/=' < test.test |\
while read index; do
    sed -i $search -e "$((index-1)) i\ <\!--" -e "$((index+8)) a\ -->" < $search
done

    The first part, `sed -n '/log4jConfigLocation/=' will get the line numbers that have 'log4jConfigLocation'. The next part uses those line numbers in two commands: insert a line 1 line above, and append a line 8 lines below.

    There is a better way using sed's hold buffer, but I'm not familiar enough with it; if you're interested, you can see this guide. Ultimately, though, if you're going to be working with this type of stuff regularly, you should check out XMLStarlet.

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