Regex Search and Replace Program

Question

Is there a simple and lightweight program to search over a text file and replace a string with regex?

Answer 1

For searching: grep - simple and fast. Included with Linux, here's a Windows version, not sure about Mac.

For replacing: sed. Here's a Windows version, not sure about Mac.

Of course, if you want to actually open up a file and see its contents while you search and replace, you can use emacs for that. Or ConTEXT. Or vim. Or what have you. ;)

See also this question.