How do I move numbers in filenames, in a batch renaming operation?

I have been trying to figure out how to rename files for the past few hours.

I have 2000 files that are like this:

file.1.pdb
file.2.pdb
file.3.pdb

I would like to rename these files to something like:

file.pdb.1
file.pdb.2
file.pdb.3

If you have rename installed, you can use

rename -n 's/(\.\d+)\.pdb$/.pdb$1/' *.pdb   # just watch what WOULD happen
rename    's/(\.\d+)\.pdb$/.pdb$1/' *.pdb   # actually rename the files

The command rename can be installed via

sudo apt install rename

Through mmv (rename multiple files by wildcard patterns) it's mush easy:

mmv '*.*.*' '#1.#3.#2' *.pdb

or zmv of zsh shell; it's a module that allows to do rename; see ZMV-Examples:

zmv -w '*.*.*' '$1.$3.$2' *.pdb

Using Perl rename:

rename -n 's/(\.\d+)(\.pdb)/$2$1/' *.pdb

Quick explanation:

• *.pdb Match all files that end with .pdb. (Done by the shell)
• (\.\d+) Match a literal dot, then one or more decimal digits. The parens create a match group.
• $2$1 Reverse the first and second match groups.
• -n No action (simulate). If the output looks good, run the command again without this flag.