windows vs unix: different behaviour with exec()

abecher has asked for the wisdom of the Perl Monks concerning the following question:

I need to know if there is a solution to exec() acting differently on windows vs unix. Best way to see the difference is using 3 little perl scripts (I'm displaying them from unix with the "more" command, but they will run as-is on windows also)

-> more testexec*
::::::::::::::
testexec.pl
::::::::::::::
#!/usr/bin/perl
system("testexec2.pl");
print "Done $0\n";
::::::::::::::
testexec2.pl
::::::::::::::
#!/usr/bin/perl
exec($^X,"testexec3.pl") or print "exec failed - $!\n";
print "Done $0\n";
::::::::::::::
testexec3.pl
::::::::::::::
#!/usr/bin/perl
`sleep 3`;
print "Done $0\n";
[download]

On unix, things act as expected: testexec.pl waits for testexec2.pl to finish (with testexec2.pl being replaced with testexec3.pl). But on windows, testexec.pl does NOT wait for testexec2.pl/testexec3.pl to finish. Is there a way to get Windows to act the same as unix? The windows behaviour does not seem correct...

FYI: I'm trying to avoid using system() instead of exec() because then I open a can of worms regarding the quoting of arguements to the programs being exec()'d (the arguements themselves may contain quotes and/or spaces, and going through the shell on the two different OS's is a whole lot of extra code I can avoid if exec() would just act right :-)

Aaron

Comment on windows vs unix: different behaviour with exec() Download Code

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Re: windows vs unix: different behaviour with exec() by almut (Canon) on Nov 19, 2008 at 20:12 UTC
the arguments themselves may contain quotes and/or spaces You could use the list variant of system, in which case the arguments won't undergo shell interpolation. `system("perl", "testexec.pl", "arg 1", '"arg2"');` [download]	[reply] [d/l]
Re: windows vs unix: different behaviour with exec() by zentara (Cardinal) on Nov 19, 2008 at 20:10 UTC
See How does system(1,"foo") work on Windows?.... you may need the weird windows "system(1,prog.pl)" to return control properly to the calling script. I don't use windows, so I'm not sure. I'm not really a human, but I play one on earth Remember How Lucky You Are	[reply]
Re^2: windows vs unix: different behaviour with exec() by rovf (Priest) on Nov 20, 2008 at 15:16 UTC
you may need the weird windows "system(1,prog.pl)" Is this an undocumented feature of Perl? Because system doesn't mention it, although it works (as I found by trying it out). -- Ronald Fischer <ynnor@mm.st>	[reply]
Re^3: windows vs unix: different behaviour with exec() by almut (Canon) on Nov 20, 2008 at 15:49 UTC
... semi-undocumented :) (as people don't usually look there...)	[reply]
Re^3: windows vs unix: different behaviour with exec() by zentara (Cardinal) on Nov 20, 2008 at 15:51 UTC
It's just one of those tips that floats around Perlmonks.... I couldn't even find it on google. I'm not really a human, but I play one on earth Remember How Lucky You Are	[reply]
Re: windows vs unix: different behaviour with exec() by wol (Hermit) on Nov 20, 2008 at 15:03 UTC
IIRC, the problem would be the way that exec() is emulated on Windows - it spawns a new process to run the command you specify and exits the current one (it does this because there's no way to re-use the existing process to run the new command). Most of the time, this implementation is indistinguishable from the UNIX-like exec(), but as you show, not always. As noted by almut, I think your best bet may be to use system() with a list. -- .sig : File not found.	[reply]