Command Line Tip: Lowercase all file names in a given directory

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

Break down:

for file in *:

For 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:']):

1. Run translate characters (tr) command to translate upper case characters to lower case characters
2. Then move the original file name to the one outputted by the tr command
3. You’re done! Celebrate