How to detect that no one is writing to a file in Linux?

Question

I am wondering, is there a simple way to tell whether another entity has a certain file open for writing? I don't have time to use iNotify continuously to wait for any current writer to finish writing. I need to do an intermittent check. Thanks.

Answer 1

What exactly are you doing where you "don't have time to use iNotify continuously"? First, you should be using the IN_CLOSE_WRITE flag so that iNotify just make one notification when the file gets closed after being written. Using it continuously makes no sense. Second, if your timing is that critical, I'm thinking writing to a file isn't your ideal solution. Do you control the first writer? Do you have to worry about anything else writing to the file after the first writer closes it?

Answer 2

lsof LiSts Open Files. fuser also works similarly (File USER), by telling you which user is using the file.

See: http://www.refining-linux.org/archives/23/16-Introduction-to-lsof-and-fuser/