Find and replace text within multiple files

Here I use sed to replace every occurrence of the word "cybernetnews" with "cybernet" in every file with the extension, c, in the directory, /home/user/directory/.

find /home/user/directory -name \*.c -exec sed -i "s/cybernetnews/cybernet/g" {} \;

A more generic variation where you search recursively from the directory of execution and operate on only regular, readable, writeable files:

find ./ -type f -readable -writable -exec sed -i "s/cybernetnews/cybernet/g" {} \;

The stream editor,sed, is a powerful utility for this kind of work and is my first choice, however, if you want to do this from an ordinary text editor using an Ubuntu based native application, I would suggest you take a look at Jedit, It is available in the repositories and can be installed by typing in your console:

sudo apt-get install jedit

Start jedit, click the search menu item, in the menu list, click the Search in Directory item, you will be presented with the dialog below:

This is similar to that of Notepad++ and does the same thing, I believe this is what you want.

Another GUI option is regexxer: