UBB.Developers Forums Community Development Programming PHP and Server-side Scripting Windows service using Perl

Ok, the last one was too easy, so here's a deep one.

I'm writing a script for backing up files daily on my computer, which is running Win2000. The "backup" consists in copying a specified list of files to a separate directory (for subsequent manual transfer to a CD).

(I know there are existing backup utilities, but I don't know of one that provides the flexibility I need, and can obtain through writing my own script.)

1) My first attempt uses the Windows task scheduler to run a Perl script (via a .bat file) every two hours. The script uses a file to keep track of when the last backup was completed. Each time the script runs, it checks to see whether a backup was done within the last 24 hours. If so, the script simply exits. Otherwise it tells me it's time to do a backup, and asks me whether to proceed. If I say "yes", it does the backup and then reports that it's done, or displays any errors that occurred. If I say "no" (because I'm in the middle of doing something else with which the backup might interfere), the script exits.

This works fine, except for one annoying problem: Each time the script runs (every two hours), a command prompt window flashes up, even if the script doesn't produce output or request input.

Someone suggested setting up the scheduled task to run as a user other than the one who's logged on. That supposedly would prevent the command prompt window from appearing. I haven't actually tried this, but I suspect that the window would not be present even if the script needed to produce output or request input, so that wouldn't work.

2) My second approach was to write a Windows service, instead of using the task scheduler.

I found a cool Perl module Win32::Daemon that makes it relatively easy to write a service.

The first problem I ran into is how to interact with the service, since it needs to tell me when it's time to do a backup, and ask me for permission to proceed. I couldn't figuring out any way of getting a command prompt window to appear. Script input/output just seems to disappear into the bit bucket (that includes Perl compilation errors as well, but that's getting off track).

I'm currently attempting to use the Perl Tk module, included with the Perl distribution I have, to interact with the user. This sort of works, but it opens another can of worms, since now I have to deal with the Tk event loop, and probably using a secondary thread to do the backup itself, which can take several minutes, all inside a service.

Does anyone have any experience with this kind of stuff that might help?

If you want to create a real Win32 Service, you should look into the ActiveState Perl Development Kit. But that's a whole other thing you'd need to worry about...

Try using wperl.exe rather than perl.exe to avoid the flashing command window in the mean time.

I run a script in the background on one of my home machines to monitor a gaming server... I didn't bother trying to do anything fancy. Just minimized the window...

Personally, I'd avoid TK if you're just using Win32... Check out The GUI Loft , a wizardish sort of thing to put together Win32 UI elements visually.

What about WxPerl ?

Also you can use this to hide the dosbox:

you can also show it again:

Wow, I figured this problem was so odd that I wouldn't get any responses, especially that quickly. Thanks

The Active State PDK, WxPerl and Win32::GUI sound interesting. I took at look at the Win32::GUI documentation, but found an article that says it wouldn't solve the flashing window problem, since the window gets displayed before the script has a chance to hide it. It looks like wperl, which I hadn't heard of before, but already exists in my distribution, is the simplest solution to my problem.

What I'll attempt is to run the two-hour task using wperl.exe instead of perl.exe, and then if the task needs to interact with me, it will "re-run itself" using perl.exe.

It works perfectly.

The task scheduler runs script #1 every two hours using wperl.exe. Script #1 checks to see a backup is due, and if so, it calls exec() to run script #2 using perl.exe. Script #2 interacts with me using its command prompt window and does the backup.

P.S. The reason I had to use exec() rather than system() was so that a new process would get created. At least, that's my guess, since when I tried to use system(), the second script appeared to run under the same Perl executable that the first script was running under.