From: Paul Archer <paul@...>
Date: 2009-07-17T11:10:51+09:00
Subject: Solved: Re: making sure a file isn't being written/copied before moving

I think I solved my problem. I was looking at inotify in order to avoid 
having the script have to check the directories on a regular basis. Turns 
out that it can report when a file is closed for writing, *and* return the 
path and basename of the file.
The only downside is that ruby-inotify doesn't (as far as I can tell) do 
recursive checks of the directory, so I'm using Open3 to call inotifywait, 
and parsing its output.

Here's my test program:

#!/usr/bin/ruby -w

require 'open3'
require 'ftools'

def inwait(path)
         Open3.popen3("inotifywait -m -r #{path}"){ |stdin, stdout, stderr|
             while line = stdout.gets
          next unless line.include?("CLOSE_WRITE")
          yield line
          end
         }
end

inwait("/tmp") do |line|
         path, action, file = line.split
         puts "path: \t #{path}"
         puts "action: \t #{action}"
         puts "file: \t #{file}"
         File.move(path+file, "/tmp")
end


Paul


Tomorrow, Paul Archer wrote:

> So, I'm (still) working on some scripts to rename and reorganize my image 
> files.
> Right now, I have a script on my laptop that pulls images off the CF card and 
> stores them locally. I have another script that rsync's the images to my 
> server at home whenever there's a connection available. These scripts don't 
> step on each other because they look at the process list for instances of 
> rsync.
>
> But I need to write two more scripts that take the image files from an 
> incoming directory, rename them, and drop them into a directory for me to 
> work on them; then once I've done whatever I'm going to do (cull, keyword, 
> etc), then I put them into a directory for archiving. The images are going to 
> be pulled from that directory, put in an archive directory, and have the 
> immutable extended attribute (xattr) set.
>
> My problem/issue is that I don't want to do anything with a file that is in 
> the process of being moved into one of these directories. I have to be sure 
> that the file is not still being moved/copied. Now, these directories are all 
> on the same filesystem, so it *should* be an atomic change by the filesystem 
> (technically a rename of the file from one directory/file name to another). 
> But I want to be sure--plus I may be dropping files into the incoming 
> directory from elsewhere from time to time. (I plan on going through my 
> backlog of old untagged files eventually.)
>
> Can someone suggest an easy (or at least reliable)  way to make sure that any 
> file I'm about to modify isn't being touched by another program?
>
> Paul
>