Last change time of a directory based on contained file contents?

Question

Is it possible to calculate the last modified time of a directory, taking changing file contents into account?

We are trying to watch a series of upload directories to determine when user FTP sessions are complete.

Users are uploading a set of files into a specific directory, and we'd like to detect when the last file within that directory hasn't changed within N minutes. (We are using this as a proxy for "FTP session is done".)

We started with this to find directories that have been idle for more than 5, but less than 10, minutes:

find . -mmin +5 -mmin -10 -type d -ls

The directory timestamp used here is based on the time the most recent file was added to the directory.

I have read Directory last modified date and it is clear that reading the mtime or mmin for the directory won't work since it doesn't change when files within the directory have their contents updated. Thus, the above won't work because if that last file is a large file that may take > 10 minutes to upload then the directory won't really have been idle (i.e. all files unchanged) when this triggers.

Are there a shell-based alternatives (ideally a configuration of the find command) that use the mtime of the last changed file inside as the timestamp, but still operate at the directory level (i.e. we don't want to get multiple hits based on all the files inside a single directory)?

Answer 1

I'm also on the "alternate solution" side of the fence.

If you have access to your FTP server's log, I suggest tailing that log to watch for successful uploads. This sort of event-triggered approach will be faster, more reliable, and less load than a polling approach like the one described in your question.

The way you handle this will of course depend on your FTP server. I have one running vsftpd whose logs include lines like this:

Fri Mar 23 07:36:02 2012 [pid 94378] [joe] OK LOGIN: Client "10.8.7.16"
Fri Mar 23 07:36:12 2012 [pid 94380] [joe] OK UPLOAD: Client "10.8.7.16", "/path/to/file.zip", 8395136 bytes, 845.75Kbyte/sec
Fri Mar 23 07:36:12 2012 [pid 94380] [joe] OK CHMOD: Client "10.8.7.16", "/path/to/file.zip 644"

The UPLOAD line only gets added when vsftpd has successfully saved the file. You could parse this in a shell script like this:

#!/bin/sh

tail -F /var/log/vsftpd.log | while read line; do
  if echo "$line" | grep -q 'OK UPLOAD:'; then
    filename=$(echo "$line" | cut -d, -f2)
    if [ -s "$filename" ]; then
      # do something with $filename
    fi
  fi
done

It's not the fanciest shell script, and to be honest I'd probably write it a little differently if I were using it myself, but this illustrates the idea well enough.