Why does sed require 3 backslashes for a regular backslash?

Question

I\'m curious, why does sed need 3 \\ just to recognize one? I\'d understand it needing 2, but 3 I don\'t.

EDIT: here\'s an example on my Windows compute

Answer 1

Your shell (probably bash) is doing its own escaping, and that's confusing you. You can use an echo command to see what is being passed, or it's easy to write a custom program (commonly named "showargs" or similar):

$ echo "s/\\\/\//"
s/\\/\//
$ echo "s/\\/\//"
s/\/\//

You can also use single quotes, which are treated differently in bash.