When you have to deal with shell scripting and task automation you need powerful tools.

I will post some basic usage examples to prove how useful sed can be when you have to modify a large number of files.

Here the simple one.
You have several files and you want a word replaced in all of them.

sed -i 's/apache2/httpd/g' files*.conf

This will modify the file matching the pattern files*.conf replacing “apache2″ with “httpd”
Removing -i will print the result on the console.

Now, the really useful one, the one that will save you a lot of time.
The problem you have is: 100+ config files that needs to be modified by adding four lines in a special position in the files.

sed -i '/RewriteEngine/i \
\n<Location \/aaa>\n\tProxyPass ajp\:\/\/127.0.0.1\:8019\/aaa\n\tProxyPassReverse ajp\:\/\/127.0.0.1\:8019\/aaa\n\<\/Location\>\n' files*.conf

-i will modify the files by adding before “RewriteEngine" the text:


empty line
<Location/aaa>
<tab>ProxyPass ajp://127.0.0.1:8019/aaa
<tab>ProxyPassReverse ajp://127.0.0.1:8019/aaa
</Location>
emptyline

Now think about adding these lines in every single file, one by one, from 1 to 100, each in an exact position, some of the configs having two or more sections to be added.

Piece of cake with sed.

Have fun with the new AC/DC album ‘Black Ice’.
You can listen and watch the video in Excel:

Via: http://www.techeblog.com/index.php/tech-gadget/ac-dc-music-video-recreated-in-microsoft-excel

The excel file is here: http://www.acdcrocks.com/excel/

Rock on!

Metallica-country version in Bulgaria (violin + accordion)