If you are running under a Unix OS, you can use a utility called "lsof" to determine what processes currently have the file open, and the mode used, etc. My lsof binary points to the URL ftp://vic.cc.purdue.edu/pub/tools/unix/lsof, if your system doesn't have it. The exit status of this program is 0 if any programs have the file open.
I really think this is kind of a crappy solution, though, because other programs may have that file open for other reasons that might not be easy to differentiate, and (as mentioned elsewhere), it doesn't help you if the FTP process legitimately closes the file in an incomplete form. | [reply] |
Using lsof is not safe, ftp may release the file if the connection is broken an reaquire later this happens seamlessly from the users perspective. It is also not supported by all unix.
The only 'safe' way to do this is to do what merlyn suggests. However if you cant rename then you could upload an empty file after the upload is complete and poll waiting for the control file to arrive, as soon as it arrives you know the preceeding download is complete.
--
Zigster
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There's no way. You cannot know if it's open. All you can do is quarantine any file touched in the last 15 minutes or so.
Some problems cannot be solved within the requirements specified.
-- Randal L. Schwartz, Perl hacker | [reply] |
That isn't true if you broaden your toolset: utilities like fstat (on BSD), fuser (on Solaris), and lsof (on a wide variety of UNIX(ish) platforms, including the aforementioned) will all quite happily tell you whether a file is currently in use ...
perl -wle '@open = qx|fstat $ARGV[0] 2>/dev/null|; print "YES" if $#open > 0' somefile
(Error checking, and use strict;'ness left as an exercise to the reader. ;)
Unfortunately, because all of those only give you a snapshot of how things looked, none of them are going to help tell whether a file is incomplete or allow you to easily deal with the race condition that follows testing (ie, what if someone resumes an incomplete upload?), but that may be a more acceptable margin of error depending on your circumstances.
Another possibility lies with some of the more advanced (?) ftpd like NcFTPd, which supposedly support event reaction and/or notification. Theoretically, that means you could have the server kick off other processes when it thinks the files are finished uploaded instead of polling every half hour.
--Kanji
Update: D'oh! Didn't see Fastolfe's response before I wrote this ... that'll teach me to post before reading the entire thread.
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[d/l] |
Well I'd like to thank everyone for their input. I had rooted through various sources and didn't find any easy solutions and I was hoping there was an obviously easy one that I just couldn't put my finger on. It looks like even though I can get perl to make coffee for me in the morning, it's not going to grind the beans for me ;) It looks like suggestions are saying I'll have to do this from more of a OS based standpoint which is where I was thinking it was going to need to go. Thanks all... for all the feedback
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If you really do have to get them as soon as they are
finished, this sounds like a project for a secure web
server. Of course, that won't work for dialin folks, but
could be a good solution.
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