How to delete empty lines in a file using Emacs?

Question

In Emacs, how to remove all empty lines (including tabs and spaces) in file?

Can M-x replace-regexp do the trick?

I can find the empty lines with regexp: ^[st]*$, but don't know how to replace it by deleting.

Answer 1

M-x flush-lines RET ^[[:space:]]*$ RET is probably the canonical way to do that.