How to switch/rotate every two lines with sed/awk?

Question

I have been doing this by hand and I just can\'t do it anymore-- I have thousands of lines and I think this is a job for sed or awk.

Essentially, we have a file lik

Answer 1

For the first part of the question, here is a one way to swap every other line with each other in sed without using regular expressions:

sed -n 'h;n;p;g;p'

The -n command line suppresses the automatic printing. Command h puts copies the current line from the pattern space to the hold space, n reads in the next line to the pattern space and p prints it; g copies the first line from the hold space back to the pattern space, bringing the first line back into the pattern space, and p prints it.