FTP users details creation

[JuanCar]

API for create FTP accounts does not work in Linux system (!!!!) and the workaround published doesnot work
The commandline cannot be run from web.
Then I try to create FTP accounts for subdomains by an script of mine. So I need some info:
What steps follows Plesk to create FTP accounts? is it enough write the record in sysusers an ftpusers tables?

Thanks