EXEC() and ncftpd commands

[Anon]

Here is my situation. I have a class of 25 students. I want to use PHP to let them execute ncftpd_passwd commands. Namely I want them to be able to set up their own accounts. I'm not too concerned about this since these are virtual users and will be restriced to their home directories. They will also be in a group which is very resrticted.

<?php
mkdir("path/$username", 0774);
exec(???);
?>

Is an idea I wan to use.
The ncftpd_passwd uses swtiches etc to do multiple functions.

The format is
root# ncftpd_passwd -f path/to/dbfile switches "username:password:UID:GID:REAL Name:other stuff:etc:etc"

This adds a user to the db virtual user file.

There is however a second way which you can create a text file and then tell ncftpd_passwd to import it as the user file. What is the correct way to get ncftpd_passwd to run from PHP. I've real a ton of forums and have had no sucess in gaining concept to start writing the correct code. Could you discuss permissions etc if you respond to this.

Thanks in advance.
Robert