On Linux, you can use Vim in conjunction with ack to search through code bases. ack is the spiritual successor of grep, and is focused on working with code. Install it using your favorite package manager; here's an example of using apt-get:

$ sudo apt-get install ack-grep

For example, you can now use ack from the command line to search for all Python files recursively (starting in the current directory) containing the word Animal:

$ ack --python Animal

The preceding code will produce output similar to grep:

Vim has a plugin that integrates the result of ack in Vim's quickfix window (see the Quickfix List section in Chapter 5, Build, Test, and Execute, to learn more about quickfix). The plugin is available from https://github.com/mileszs/ack.vim. After installation, you will be able to execute :Ack from Vim:

:Ack --python Animal

This will run ack and populate the quickfix window (see the preceding section, as well as Quickfix List in Chapter 5, Build, Test, and Execute, for more information about a quickfix window) with the output: