Mass Rename File Extensions

March 19, 2008

I recently had to rename somewhere in the neighborhood of 100+ files as I was moving code from one platform to another. Obviously, I was looking for a quick solution, and what follows is the shell (Bash) script that I used to do the job:

#!/bin/bash
#
# Rename filename extensions:
#
# Example: ./ren txt xml
#
# Script needs to be set as executable using:
#   > chmod a+x ren
#

# There must be two command line parameters
# If not, display message and exit
if [ $# -ne 2 ]
then
  echo Usage: $0 old_extension new_extension
  echo Example: $0 txt xml
  exit 1
fi

# How many file were renamed
filecount=0

# For each matching extension...
for filename in *.$1
  do
    # Move file Strip off part of filename matching 1st argument,
    # then append 2nd argument.
    mv $filename ${filename%$1}$2
    ((filecount++))
  done

echo Renamed $filecount files

exit 0

To use the script, save the code to a file (I used the name ren) and change the file type to executable as follows:

chmod a+x ren

With that, you can now change a group of file extensions in one fell swoop. For example, to change all files with the extension txt to xml:

./ren txt xml

A screenshot follows of the script in action.

Rename

The work horse behind all this is known as parameter expansion. You can learn more by following any of the links below:

4 comments

This doesn’t work if there are spaces in the file names, like in music

by Anonymous on May 18, 2008 at 4:06 pm. Reply #

To work with spaces, put ” in line 28, so it will be:

mv “$filename” “${filename%$1}$2″

by Everson Santos Araujo on May 22, 2008 at 8:18 am. Reply #

this is not worth a shell script — just type it in by hand

for i in *.txt; do mv $i `basename $i .txt`”.xml;done

of course, that doesn’t handle spaces right, so fix up the rest

for i in *.txt; do base=`basename “$i” .txt`; mv “$i” “$base”.xml;done

– peter

by peter honeyman on Jun 9, 2008 at 8:27 am. Reply #

For some odd reason I had to change Peter’s second one to:
for i in *.mpeg; do mv “$i” “${i%mpeg}mod”;done

(I’m changing mpeg extensions back to mod so I convert them to dv files for Final Cut Pro X)
Oh, using Mac OSX Lion

By far the best, quickest ánd cheapest solution to change file extensions in batch on a Mac! Thanks!!

-Jan

by Jan on Dec 27, 2011 at 2:52 pm. Reply #

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