Change files extensions

Simple example of bash script that is changing files extension in desired directory:

#!/bin/bash

CURRENT_EXTENSION="${1-mp3}"
NEW_EXTENSION="${2-mp4}"
FILES_PATH="${3-$PWD}"

FILES_LIST=$(find ${FILES_PATH} -maxdepth 1 -name "*.${CURRENT_EXTENSION}")

for FILE in $FILES_LIST; do
    NEW_FILE=$(echo "$FILE" | sed "s/${CURRENT_EXTENSION}/${NEW_EXTENSION}/")
    echo "Renaming file: $FILE -> $NEW_FILE"
    mv $FILE $NEW_FILE
done

Usage

You can use it by simple executing file:

./change_ext.sh

It will be executed with default settings: extensions to change: mp3, new extension will be mp4 and script will look for files in current directory.

It is also possible to overwrite settings:

./change_ext.sh csv txt /tmp

It will change all csv extensions to txt in /tmp directory.