system() - return value always -1

[Bob B]

Snippet from my .pm :

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        @cmd = ("sudo", "/opt/energenie/RobBoilerControl.py", "ch", "on"); #MUST use sudo - no other method works reliably to access /dev/mem
        $retVal = system(@cmd);
        Log 3, "retVal = $retVal";
        #system(@cmd) == 0 or Log 3, "system @cmd failed: " ; # test fails - system always returns -1 ?
        #or die "system @cmd failed: $?";       

system(@cmd) works fine but always returns -1 instead of 0. (I have since seen reference to this behaviour in fhem forum somewhere but have lost it now.)
I want that return value! The script's output end's up in the log very nicely and I don't want to rewrite it so as to run it with backticks but that's all I can think of right now.
Any thoughts please?

[rudolfkoenig]

I get -1 if perl cannot execute the program.
I tried it with test.x:

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#!/bin/sh
echo hallo
exit 7

and

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perl -e 'my @a = ("test.x"); my $v = system(@a); printf "%04x\n",$v'
which returns

hallo
0700

[Bob B]

Thanks Rudolf.

Running perl directly is no problem; I get exactly the same behaviour with system() as you do - with correct status returns.

Running system() inside fhem  (99_RobBoilerControl.pm in my case) it always returns -1 even though the associated python script succeeds.

I'm too much of a noob in fhem and perl to guess what is going wrong.

Bob