Self Updating Exe par on Windows

Question

I am trying to create a script that will "self update" when it detects a new version on a server. Initially the idea I had was, when a new version is detected, download the file, then starts a DOS batch file that simply overwrites the original exe with the new one. I thought, that I could use sytem(start update.bat ) then immediately exit 0; The .bat file waits for a couple seconds, and then tries to delete the old exe. This fails, I guess because even when using system(start ... ), the new "process" is actually the same process, is this correct? Is there any way to launch a completely new process from perl in windows, that would allow me to delete the .exe? Or is there a different approach that would be better?

Thanks, Eric Seifert

Answer 1

See the documentation on the Windows Restart Manager, an API introduced with Windows Vista that manages restarting applications, for updates, for you.

Answer 2

Ever heard of java WebStart? There is a PAR equivalent, PAR::WebStart Basically, you configure it, then download code live from a trusted website

so your .exe would just be a frontend to PAR::WebStart, with the real program downloaded off your website

Answer 3

I know this is an old question, but I thought I'd put my solution here since I'm working on the same sort of thing. Your batch idea is the way I went, but the small change I made was to use exec() instead of system() since the former (according to this) "...executes a system command and never returns", which seems to release the running process. This appears to work both when running interpreted Perl files with Strawberry Perl, and when running compiled programs with PAR::Packer.

I've created test.pl, which was ultimately compiled to test.exe, as follows:

#!/usr/bin/perl

use 5.10.0;
use strict;
use warnings;

    my $batch_file = <<"BATCH";
rem ### IT IS SAFE TO DELETE THIS FILE ###

\@echo off
ping 127.0.0.1 -n 2 -w 1000 > nul
echo Copying over update file...
copy testfile.exe test.exe

BATCH

    open my $fh, '>', 'update.bat';
    print $fh $batch_file;
    close $fh;

    exec( 'update.bat' );

testfile.exe is a standby "upgraded" version of test.exe, just to make sure that I can overwrite test.exe while it's running, and I can. The ping is a way to pause for 2 seconds to make sure the process has had a chance to exit before trying to overwrite the file.

Oddly enough, the created batch file update.bat can't delete itself, even though batch files can normally delete themselves. If I create a batch file with this:

start /b "" cmd /c del %0

It will delete itself without any errors. But if I include that snippet in update.bat, it complains that The process cannot access the file because it is being used by another process. I'm not sure why. Since this isn't particularly important in my application, I haven't pursued this. I just leave update.bat behind and let it be overwritten next time an update occurs. But I do notate in the file that it's safe to delete in case anyone looks at it later.