Batch change file extension

Anyone know how to do this? I am trying to rename a bunch of *.m4a files to *.m4b

any help is appreciated.

 

These might help, I'm not sure though because they seem to be talking about adding extensions, but might help nonetheless.

http://discussions.apple.com/thread.jspa?messageID=5053368

http://www.ehmac.ca/mac-ipod-help-troubleshooting/36780-adding-extensions-batch.html

Might be able to remove extension first, then add it back on with the new one.

This one might also help
http://www.macosxhints.com/article.php?story=20041215055518221

 

Try this applescript.

Code:

<START APPLESCRIPT>

set thePath to choose folder with prompt "Select folder to rename files in:"
set ext to display dialog "Extension to Replace:" default answer ""
set ext to text returned of ext
set extNew to display dialog "Replace With:" default answer ""
set extNew to text returned of extNew

tell application "Finder"
    try
        set the datlist to ¬
            ((every file in thePath whose name ends with ext) as alias) ¬
                as list -- set name criteria
    on error number -1700 from f
        set datlist to f as list
    end try
    repeat with dat in datlist --list of alias references to the files
        select file dat
        set workingName to the name of dat as text
        set theOffset to offset of ext in workingName
        set chopped to characters 1 through (theOffset - 1) of workingName
        set newName to chopped & extNew as text
        set name of selection to newName
    end repeat
end tell


<END APPLESCRIPT>