bash: Lowercase all filename in a directory with one line of code

Here’s a one-liner you can use to change all the filenames that include uppercase letters to lowercase. If I didn’t write about it, I’d forget how it works, so here we go!

$ for f in *; do echo $f; mv $f $(echo $f | tr '[:upper:]' '[:lower:']); done

Break down:

for file in *: loops over every file (variable). You could also do in *.pdf and that would only select PDF’s for example

do echo $f: do is part of the for loop syntax, echo the variable f

$ mv $f $(echo $f | tr '[:upper:]' '[:lower:'])

This command goes from inside to outside because of the parenthesis.

echo out the filename of f and pipe it to the tr command.

The translate characters (tr) translates then upper case characters to lower case characters.

Then move the original file name to the one outputted by the tr command