Append only file

I'm trying to realize a file. Each event just appends one line to the file. So far this is a no brainer. The hard part is that several users are supposed to be able to add entries to that file but no one is suppo开发者_运维知识库sed to be able to modify or delete existing ones. Can I somehow enforce this using file access rights? I'm using Linux.

Thx

On linux you have the option of using the system append-only flag. This is not available on all filesystems.

This attribute is set using the chattr utility and you should view the man page. Only root can set this attribute.

On Ubuntu you'll probably end up doing: sudo chattr +a filename

The classic permissions, read, write, and execute won't get you there. If you have write permission you can delete the file, and all the lines in it.

You'll need some kind of program to arbitrate the file access. One way would be to open up a fifo and have the producers write to the fifo. If the writes are not too big (4k writes are atomic on my linux box) the different writes won't get intermixed. By making the consumer process have priviledges that the producers don't have, the producers won't be able to see the final results.

You could use something like syslog to do this.