Perl lock file while updating dating web sites based on income
Furthermore, the lock is released either by an explicit LOCK_UN operation on any of these duplicate descriptors, or when all such descriptors have been closed. Therefore, the question then boils down to: Who should unlock the file?On Free BSD, that's apparently up to you to decide: Locks are on files, not file descriptors.update: fixed open fail check, thanks to spotter tlm I think this is one of those cases where it could make a difference if we knew: "Why do you ask?" In particular, if only the child is going to be using the locked file handle, why would you need or want to open/lock the file before forking?HTH; Hi Team, I have a requirement to access a shared resource from the user and interrupt context. -Shiva Hi all, I have to test some user priviliges.What type of locking mechanism I have to use for this. The goal is to be sure that an unauthorized user can't restart some modules (ssh, mysql etc...).
So you need to use same locking mechanism in all processes interested in locking the file, in order to ensure that files gets locked properly.To make flock non blocking you have to use the LOCK_NB flag.works like a charm, the parent grabs the exclusive lock straight away... I will not fork a flock (or flock a fork), unless in dire need of weird behaviour..Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Visit Stack Exchange Database Administrators Stack Exchange is a question and answer site for database professionals who wish to improve their database skills and learn from others in the community. Sign up to join this community I was asked how to avoid deadlocks without changing the transaction logic (I cannot commit after updating A and commit again after updating B).Perl's flock() does give you a lock on a file, if you use LOCK_EX, and all other processes use that mechanism too. If you don't want the file to be modified, change the permissions to read-only for everyone else (but root will still be able to modify it)perldoc -f flock Two potentially non-obvious but traditional flock semantics are that it waits indefinitely until the lock is granted, and that its locks merely advisory.