chris@chris-laptop:~$ which rename
/usr/bin/rename
Then use 'rename' as follows to carryout the renaming of files in your current working directory:
chris@chris-laptop:-$ sudo rename 's/.html/.php/' *html
Hope that's useful.
christo
chris@chris-laptop:~$ which rename
/usr/bin/rename
chris@chris-laptop:-$ sudo rename 's/.html/.php/' *html