[Sieve] Is the way to run external script to get attachment?

[Konstantin Shalygin]

Hello.

Read all about Extprograms, but have a question.
Use case:
Every day we have couple messages with attachment (from one sender, this 
is one-way communication). This attachment is uploads to ownCloud. By 
hand... need some automation.
As I see, pipe cat execute scripts with text data USER/FROM/SUBJECT - 
and I think with variables it can be any text data, how about attachment?

How I see this: script executes and as arg receives from sieve 
attachment file, or message file and we can parse it for attachment. 
When we have attachment - upload to ownCloud via RESTapi and purge message.

Found some realization for encrypt messages 
https://github.com/EtiennePerot/gpgit/blob/master/encmaildir.sh
but for me more easy just connect to IMAP and do what I want (but I love 
sieve).

Thanks.
<http://wiki.dovecot.org/Pigeonhole/Sieve/Plugins/Extprograms>