Quickest way to move a line in a text file before another line in a text file?

A scriptable editor makes this pretty straight-forward!

printf '%s\n' '55m22' 'wq' | ed -s input

This sends two commands to ed (editing the file named input):

  1. 55m22 -- move line 55 after line 22
  2. wq -- save the file back to disk and quit.

A little shorter:

ex input <<<"55m22|wq"

It's somewhat longer in vi than in ed:

vi input

55G ... go to line 55
dd ... delete one line
23G ... go to line 23
P ... paste the deleted line before line 23
ZZ ... write file and exit