How to batch rename files by exchanging substrings in the filenames?

Question

I have files like ABC_asd_f.txt, DEF_qwe_r.txt, ...

How can I exchange the uppercases before the first underscore with the lowercases after? So ABC_asd_f.txt becomes asd_f_ABC.txt, DEF_qwe_r.txt becomes qwe_r_DEF.txt, ...

Answer 1

Use perl rename. Firstly use the -n flag for a dry-run.

rename -n 's/^(...)_(..._.)/$2_$1/' *

Then, if you are happy, run it for real.

rename 's/^(...)_(..._.)/$2_$1/' *

Explanation

This uses capturing groups.

• rename 's/foo/bar/' *: replace foo with bar for all files *.
• ^(...)_(..._.): from the beginning of the line ^, capture the first three characters (...), skip over _, then capture the next five characters, where the fourth is underscore (..._.).
• $2_$1: replace the string above with the capturing groups reversed (i.e. the second, an underscore, then the first).

Rename version

There are two renames in Linux-land. You can tell if it's perl rename with the following

$ rename --version
perl-rename 1.9

The other one will give a different result.

$ rename --version
rename from util-linux 2.28