in reply to system and $?

To get the return value of the program, you need to check $? & 127:
system "true";
echo $? & 127;

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If you need the "result" of the system command, get the return value:
print system "does-not-exist";
print system "true";
print system "false";

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The results are -1, 0 and 256. Not really good, but here you get -1 in case of any kind of execution error.
I agree that this behaviour isn't good at all and the documentation doesn't seem to match the reality. Sorry for this.

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Re^2: system and $?
by rovf (Priest) on Aug 26, 2009 at 12:35 UTC
    you get -1 in case of any kind of execution error.

    Not on Windows 2000, as you can see from my example. I don't know about XP or Vista. Maybe someone could try this out?

    BTW, to get the return code on Windows 2000 (ActiveState Perl again - I don't know about Strawberry), you need to do a bit more logic than you posted, because you can't distinguish between a program execution error, and a program which runs fine but returns exit code 1. Here is what you have to do: 

    $!=0;
system('your_program_goes_here');
my $child_error=$? & 0xff;
my $maybe_exit_code=$? >> 8;
if($child_error || ($maybe_exit_code && $!)) {
  # there was an error in program execution
}

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    Also note that even if $?==0, it does not say that your program terminated with exit code 0. You get only the low 8 bit of the "real" Windows exit code, so if your program exited with a code which is a whole multiple of 256, you wouldn't notice it.
    -- 
    Ronald Fischer <ynnor@mm.st>
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