How can I batch rename filenames in the console

Question

I have a great number of files whose name is "img800400_497708.307247.png", and I would like to change all dots (periods) to an underscore using the console. How can I do that?

Answer 1

You can do this fairly easily with the rename command. The only problem is preserving the extension. We start by replacing all the dots, but then replace _png with .png. You'll obviously need to adapt that for other extension types.

cd /path/to/images
rename 's/\./_/g; s/_png$/.png/' *.png -vn

Note: the -vn on the end will only demonstrate what it would do. It's a safety trigger. Check the command does what you want and then remove that last part.

A super-simple test harness:

$ touch file.{01..10}.png
$ rename 's/\./_/g; s/_png$/.png/' *.png -vn
file.01.png renamed as file_01.png
file.02.png renamed as file_02.png
file.03.png renamed as file_03.png
file.04.png renamed as file_04.png
file.05.png renamed as file_05.png
file.06.png renamed as file_06.png
file.07.png renamed as file_07.png
file.08.png renamed as file_08.png
file.09.png renamed as file_09.png
file.10.png renamed as file_10.png

Answer 2

A bash solution that removes the extension, replaces the periods with underscores, then adds back the extension:

for f in *.png; do g="${f%.*}"; echo mv -- "$f" "${g//./_}.png"; done

Remove the echo once you have satisfied yourself whether it works. It could fairly easily be extended to a general .ext extension if you have more than one file type, for example

for f in *.*; do g="${f%.*}"; e="${f##*.}"; echo mv -- "$f" "${g//./_}.$e"; done