Allow users to update a single file on my http server

Question

I have an XML file on my http server. I have full root access to the server (the server is running ubuntu). What I want to do is allow some users to append to the xml file. I am looking for a secure way to do this, so that the user can only append one line to the file in a specific format. What would be the best way to go about this? I am assuming I would have to give people guest access to do this but how will they gain write access to the file?

Answer 1

chattr +a filename

This makes the file append only.

OR

You may also want to consider just writing a script which will take some input and append it to the file. That way you don't need to give everyone privileges to edit your file, just the script which runs at the level of the apache user. With a script you can also check the input to make sure it is valid.