That is not the right way to think about it. HTTP has nothing to do with FTP.
A machine cluster has users.
An FTP server daemon allows users to upload and download files within their home directories.
An HTTP server daemon serves a web site by looking for files inside a specific directory called a document root.
More than one web site can have the same document root, but there is only one document root per web site.
And the document root will reside in the home directory of a single user of course.
Have you heard of permissions and user groups yet?
Yes and no. Plain FTP access is restricted to the home directory of the user you logged in as - meaning to use FTP both ways, you have to download the file from logged in as one user then upload it after logging in as the other user. Using SFTP you would still have to download and upload, but you only need to login as the user you need to upload to.
Yes, theorectically. I code in Perl and would have no problem sharing files between users.
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