[TriLUG] Scheduling file transfers

[Jeff Groves]

Mark Freeze wrote:

>A year or so ago I had a problem downloading a file via ftp onto a
>Windows box with WS_FTP.  The file was about 100MB and I started
>downloading the file while my customer was still uploading, so I only
>got about half of the file.  WS_FTP allowed me to do this with no
>error. (Which I thought was kinda crazy.)
>
>Now I have an offsite ftp spot that my customers use to send me files
>at random times during the day. I want to automatically download and
>process these files onto my box as soon as they appear on the site so
>I was thinking that I would scehedule up a cron job to look for these
>files every 10 min. When I do this am I going to have the problem of
>seeing the file and trying to get it as they are uploading?  Some of
>these files are over 100MB and might take my customer a while to
>upload.  Someone told me to make sure that I have exclusive access to
>the file before I download it, but since I have no control over the
>ftp server I'm not sure on how to accomplish that task.
>
>Any help will be greatly appreciated.
>
>Regards,
>Mark.
>  
>
On the subject of knowing when to grab the file so that you aren't using 
an incomplete file, what you would want the sending process to do is to 
send a second file to use as a semaphore for your process.  So, that 
just after it sends you the file that you are interested in have it send 
you a small file that will signal your process that the first send it 
complete and that you can be assured that the file was sent in 
entirety.  Then have your process delete the semaphore file when it is 
done processing the large file.

Jeff G.

-- 
Jeff Groves
email: jgroves at krenim.org             Web Site: http://www.krenim.org/
blog: http://blogs.krenim.org/Jeff