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

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

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 as sed or awk.

For example, I believe this sed command should swap lines 14 and 26 in a single file:

sed -n '14p' infile_name > outfile_name
sed -n '26p' infile_name >> outfile_name

How can this be extended to work on multiple files? Any one-liner solutions welcome.

Solution

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

# or as multiple lines:

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.

Alternative:

sed -Ei '10{:a;N;15!ba;s/([^\n]*)(.*\n)(.*)/\3\2\1/}' file1 file2 filen

Another using parallel, bash and ed:

parallel "ed -s {} <<<$'7m5\n5m7\nwq'" ::: file1 file2 filen