How to determine if a file is in use
russell.don at gmail.com
Wed Nov 4 05:38:58 UTC 2009
On Tue, Nov 3, 2009 at 20:49, Cameron Simpson <cs at zip.com.au> wrote:
> On 03Nov2009 13:31, Donald Russell <russell.don at gmail.com> 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
> | 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.
> I liked the upload-then-rename suggested by another poster, if you can
> get this implemented.
> | I could also configure the ftp server to lock files being written, but
> | seems to be discouraged. (based on man vsftpd.conf)
> It's not discouraged for any reason that seems to match your use case.
> You've got a well defined upload area and no malicious users.
> Use the lock facility! That's what it's for!
> | 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
> Do it! See above! Have you tried it?
Thank you all for some great suggestions.... :-)
Based on the feedback I've received, I'm going to ...
1 - configure vsftpd to lock files while writing (no malicious users etc)
2 - use ftp put/rename like put ftp-in-progress.foo.bar / rename
ftp-in-progress.foo.bar foo.bar because it provides such a great "visual"
for watchers, and a convenient way to determine which files are "in transit"
and which are complete.
3 - use lockfile/fuser to ensure my cron job doesn't start processing a file
that's already being read by an earlier cron job.
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