On Tue, Nov 3, 2009 at 20:49, Cameron Simpson <cs@zip.com.au> wrote:
On 03Nov2009 13:31, Donald Russell <russell.don@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 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.

I liked the upload-then-rename suggested by another poster, if you can
get this implemented.

Otherwise...

[...]
| I could also configure the ftp server to lock files being written, but that
| 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?

Cheers,



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.

Cheers