How to determine if a file is in use

[Patrick O'Callaghan]

On Tue, 2009-11-03 at 19:23 -0800, Richard England wrote:
> On 11/03/2009 01:31 PM, Donald Russell wrote:
> > Another system uses FTP to drop files in a directory for me to process.
> > I have a bash script to process the incoming files. The script is 
> > started by cron periodically.
> >
> > There's a problem if the FTP transfer is still in progress because the 
> > process begins reading the file even though it isn't complete yet.
> >
> > From a bash script, is there a way to tell if the file is still being 
> > written to?
> > I was looking at the lsof command, which will tell me if the file is 
> > opened or not, so that's a possibility... but it sure seems awkward 
> > for the task.
> >
> > I could also configure the ftp server to lock files being written, but 
> > that seems to be discouraged. (based on man vsftpd.conf)
> >
> > Basically, what I want is something like
> > Can I get an exclusive read on file x?
> > No - skip that file, go onto the next one
> > Yes - start processing that file
> > (I'm not concerned about the possible race condition there... I have 
> > other protections for that)
> >
> > Thanks for any suggestions...
> >
> >
> >
> 
> Perhaps "fuser" might be of use?

Duh! I had a nagging feeling that lsof wasn't the best answer, it's just
that I've been obsessing about it recently :-)

File locking is unimportant for the OP's application. If fuser says the
file's still in use, just postpone for another cycle. Presumably the
same file isn't going to be overwritten by another ftp process before it
has a chance to be read.

poc