Bash Script To Change File Extensions


Ever want to change the file extension for a group of files in one fell swoop? Me too. If you are using a unix-like system (Linux, Solaris, OS X, etc) then this is extremely easy using a Bash script. If you are on a Windows system then stop everything right now and go install the Cygwin environment.

The task at hand is actually pretty easy and can be done as a one liner, but I thought I’d create a more general purpose script. That way I can just use my script the next time I need to rename some files.


find "${1}" -iname "*.${OLDEXT}" |
while read F
  echo "mv \"${F}\" \"${NEWFILE}\""
  mv -f "${F}" "${NEWFILE}"

The numbers 1, 2 and 3 represent command-line arguments. You’ll see above the first thing I do is store the 2nd argument as the old extension and strip off any leading “dot”. I do the same with the 3rd argument storing it as the new extension. Next I do a find with the first argument being the search directory. Notice the iname option which means it will do a case insensitive name match. I pipe the results of the find into a while loop, calculate the new filename and rename/move the file. That’s it! Below is the full script file which includes a usage statement and some pretty comments.

Note: if the file here doesn’t work for you then you may simply need to retype it. I created the file on a Cygwin environment in Windows and sometimes when you move files from Windows over to a Unix system there are special characters which prevent it from being executed.