Как установить Ubuntu на поток HP 13?

Версия, использующая rename, которая работает для вашего измененного формата, будет

rename -- 's/(\.in|\.out)\.(\d+)/$2$1/' *

, например

$ ls
txt.in.1  txt.in.2  txt.in.3  txt.out.1  txt.out.2  txt.out.3
$
$ rename -nv -- 's/(\.in|\.out)\.(\d+)/$2$1/' *
txt.in.1 renamed as txt1.in
txt.in.2 renamed as txt2.in
txt.in.3 renamed as txt3.in
txt.out.1 renamed as txt1.out
txt.out.2 renamed as txt2.out
txt.out.3 renamed as txt3.out