To flock or lock??

[martymart]

Fellow Monks

Its a real newbie question, but here goes...
I want to edit raw xml files from a form text area. Opening the valid file, and saving are not a problem. Its for an intranet with very limited users, so I am not so much concerned with security issues. However, I am concerned with the same file being opened by multiple users. Can anyone explain to me why I should (or not) use the flock function. Or would using the get_lock/unlock functions (with a sacrifice file) be the preferred practice ?

Many Thanks,
Martymart.

[Abigail-II]

Since when does Perl have get_lock/unlock functions?

As for whether or not, and if yes, how, you should use flock depends on what you are exactly doing. Normally you need to flock files if there's a change that if one process is modifying a file, another process is accessing the file (be it for reading or writing). The syntactical details about file locking can be found in perldoc -f flock and in man perlipc.

Abigail

[hardburn]

Personally, for any bit of file handling code I write, I always get a shared lock if I'm reading it, and an exclusive lock if I'm writing/appending (unless this is just a quickie script that will never be used a second time). This does introduce a performance hit, but if that becomes an issue, it's a matter of commenting out one line.

I do this mostly as a means of covering myself. If someone else writes a program that also works with this file, and this file gets messed up because they didn't lock it, I can say: "I did my part. If you didn't do yours, that's not my fault."

----
Reinvent a rounder wheel.

Note: All code is untested, unless otherwise stated