Rename all items in a directory to lower case

5 
 $ for i in *; do mv "$i" "${i,,}"; done

April 20, 2013, 9:41 p.m. — EvaggelosBalaskas

Explanation

Loop over the items in the current directory, and use Bash built-in case modification expansion to convert to lower case.

Limitations

The case modification extension is available since Bash 4.

Related one-liners

2

Rename all files in a directory to lowercase names 

 $ paste <(ls) <(ls | tr A-Z a-z) | while read OLD NEW; do echo mv -v $OLD $NEW; done

Aug. 5, 2011, 8:57 p.m. — Janos

Explanation

  • <(cmd) is the filename of a named pipe (FIFO), where the named pipe is filled by the output of cmd
  • paste puts together the named pipes to form two columns: first column with the original filenames, second column with the lowercased filenames
  • ... | tr abc ABC transforms stdin by replacing any characters that appear in the first set of letters to the second set of letters
  • while read old new; do ...; done for each line it reads the first column into $old and the second column into $new

Limitations

  • Won't work if there are spaces in a filename.