Renaming Groups of Files From the Command Line

First, if I said "longest" I mis-spoke: "#" and "%" remove the "shortest" match, "##" and "%%" remove the longest match.

The rename command is this:

   mv -i $f 2009${f#*-2009}-${%-2009*}

There are 4 parts to the final file name:

   2009                # Literal
   ${f#*-2009}         # Based on original name
   -                   # Literal
   ${f%-2009*}         # Based on original name

Given the name "aa-2009-01-01". The first substitution removes the shortest prefix that matches "*-2009", in this case that prefix is "aa-2009", leaving "-01-01". The second substitution removes the shortest suffix that matches "-2009*", in this case that suffix is "-2009-01-01", leaving "aa". So the final name is formed from:

   2009                ==> 2009
   ${f#*-2009}         ==> -01-01
   -                   ==> -
   ${f%-2009*}         ==> aa

Resulting in the file name "2009-01-01-aa", the desired result.

Rename will work for you in some cases but not all, specifically it wouldn't work for the example in the video, unless I'm missing something...