unrar folder with password (terminal)

From man unrar:

-p<password>
  Set password.

So your line would be something like:

for file in *.part01.rar; do unrar x -p<password> ${file}; done;

I only unrar the first part (when there are part01.rar, part02.rar, etc.) and it goes itself for the rest of the files.

unrar x An_Awesome_Movie.part01.rar -ppassword