The Silver Searcher is very good for using the terminal as an IDE.

I have two aliases which I find very helpful.

- Search Obj-C files:

  alias ago='ag -G ".*\.(h|m)"'

- Search Ruby files:

  alias agr='ag -G ".*.rb"'

Also if you are looking for an alternative to sed don't miss replace[1].

[1] https://github.com/harthur/replace