如何在将文件添加到目录时运行Windows批处理或Perl脚本？

Question

I am trying to write a script that will parse a local file and upload its contents to a MySQL database. Right now, I am thinking that a batch script that runs a Perl script would work, but am not sure if this is the best method of accomplishing this.

In addition, I would like this script to run immediately when the data file is added to a certain directory. Is this possible in Windows?

Thoughts? Feedback? I'm fairly new to Perl and Windows batch scripts, so any guidance would be appreciated.

Answer 1

You can use Win32::ChangeNotify . Your script will be notified when a file is added to the target directory.

Answer 2

It wouldn't be too hard to put together a small C# application that uses the FileSystemWatcher class to detect files being added to a folder and then spawn the required script. It would certainly use less CPU / system resources / hard disk bandwidth than polling the folder at regular intervals.

Answer 3

Checking a folder for newly created files can be implemented using the WMI functionality. Namely, you can create a Perl script that subscribes to the __InstanceCreationEvent WMI event that traces the creation of the CIM_DirectoryContainsFile class instances. Once that kind of event is fired, you know a new file has been added to the folder and can process it as you need.

These articles provide more information on the subject and contain VBScript code samples (hope it won't be hard for you to convert them to Perl):

• How Can I Automatically Run a Script Any Time a File is Added to a Folder?
• WMI and File System Monitoring

Answer 4

The function you want is ReadDirectoryChangesW . A quick search for a perl wrapper yields this Win32::ReadDirectoryChanges module.

Your script would look something like this:

use Win32::ReadDirectoryChanges;

$rdc = new Win32::ReadDirectoryChanges(path    => $path,
                                       subtree => 1,
                                       filter  => $filter);

while(1) {
    @results = $rdc->read_changes;

    while (scalar @results) {
      my ($action, $filename) = splice(@results, 0, 2);
      ... run script ...
    }
}

Answer 5

You can easily achieve this in Perl using File::ChangeNotify . This module is to be found on CPAN: http://search.cpan.org/dist/File-ChangeNotify/lib/File/ChangeNotify.pm

You can run the code as a daemon or as a service, make it watch one or more directories and then automatically execute some code (or start up a script) if some condition matches.

Best of all, it's cross-platform, so should you want to switch to a Linux machine or a Mac, it would still work.

Answer 6

You need to consider what is a sufficient heuristic for determining "modified".

In increasing order of cost and accuracy:

1. file size (file content can still be changed as long as size is maintained)

2. file timestamp (If you aren't running ntpd time is not monotonic)

3. file sha1sum (bulletproof but expensive)

I would run ntpd, and then loop over the timestamps, and then compare the checksum if the timestamp changes. This can cover a lot of ground in little time.

These methods are not appropriate for a computer security application, they are for file management on a sane system.