Is there a good way to implement file updating? such as lock, update, reload...

[Diez B. Roggisch]

Evan wrote:

> Hello -
> 
> My script use a DB file which is written by XML,  and the user load
> this DB file (XML tree in memory), and then do some updating about
> this tree, such as delete element, generate new element or move
> element.
> 
> The thing is, my script is a cmd based program (based on module
> "cmd"), and there are many users would use this script at same time,
> in a shell style prompt (module "cmd"), so I want to implement a
> updating after a user update the XML tree,  it such as a "signal
> console",  so that all the user can keep same DB, or other user can
> see update a few seconds later.
> 
> What I did is, create a new file calling "db_change", and put a number
> "1" in file, and then update the real "DB" file (by change uid to lock
> file), other user to check this file and then re-load XML file,  but I
> do not think it is a good idea, the performance is not good.
> 
> I would like to know if you could help on this matter, I hope I can
> get inspiration/example from you guys.

Start using a proper database. And get rid of the XML. If you need it for
output/exchange purposes, generate it from the DB.

Diez