Unix Third Edition: Visual Quickstart Guide

Using ROT₁₃ Encoding with sed

In Usenet newsgroups (among other places), text is often encoded with something called ROT13, which is an abbreviation for “rotate (the alphabet by) 13.” That is, A becomes N, B becomes O, and so forth. If text is encoded, people have to take extra steps to decode the message. For example, if a message includes an offensive joke, people who don’t want to see the joke won’t have to. Similarly, if the message is a movie review, people who don’t want to know the ending won’t have the surprise spoiled. Instead, the message encoded with ROT13 might look like this:

Tbbq sbe lbh--lbh svtherq vg bhg! Naq ab,
gurer'f ab chapuyvar. Ubcr lbh rawblrq
gur obbx! Qrobenu naq Revp

A great way to use ROT13 encoding (and decoding) ...