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

With GNU awk:

awk '
FNR==NR {if(FNR==14) x=$0;if(FNR==26) y=$0;next} 
FNR==14 {$0=y} FNR==26 {$0=x} {print}
' file file > file_with_swap