swap fields in file names

Question

How can I do the following change in file names. I suppose this is possible with rename, but I do not know how.

A_B_C.pdf

to

C_A_B.pdf

A, B and C are different words in my file names, like Complete_Works_Plato.pdf, for example.

Answer 1

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

• [^_]* Any number of non-underscores.
• ( ) Captures a group. The 1st pair is reproduced by $1 and the 2nd pair by $2.

Remove the -n if you are satisfied with the output.

A similar approach with shell script:

for file in *.pdf; do
    f12=${file%_*}
    f3=${file##*_}
    f3=${f3%.pdf}
    mv -- "$file" "${f3}_${f12}.pdf"
done

In parameter expansion you find the meaning of % and ##.