Unix one-liner to swap/transpose two lines in multiple text files?

Question

I wish to swap or transpose pairs of lines according to their line-numbers (e.g., switching the positions of lines 10 and 15) in multiple text files using a UNIX tool such a

Answer 1

This might work for you (GNU sed):

sed -ri '10,15!b;10h;10!H;15!d;x;s/^([^\n]*)(.*\n)(.*)/\3\2\1/' f1 f2 fn

This stores a range of lines in the hold space and then swaps the first and last lines following the completion of the range.

The i flag edits each file (f1,f2 ... fn) in place.