monk2b has asked for the wisdom of the Perl Monks concerning the following question:

I like to test the error status of system() when I use that function. Recently I had reason to use the module Net::SSH:Expect in a program of mine. I have noticed that the value of $? after a system() call has changed to -1.

If I comment out the line "use Net:SSH:Expect" I get the results I am use to seeing a 0 for no error and 256 for error. If I uncomment "use Net::SSH:Expect" the value of $? is -1 on error or success. I am not sure what the real issue is here. Any info would be appreciated.

This is a simplistic code example of what is happening.

Bob 
#!/usr/bin/perl

use strict;
use warnings;
use Net::SSH::Expect;


my $command0 = "ls -l /tmp";
my $command1 = "ls -l /temperature";
RunCmd();

sub RunCmd{
system("$command0 > /dev/null");
print "System status info is $? \n";
system("$command1 > /dev/null 2> /dev/null");
print "System status info is $? \n";
}

[download]
I got 99 problems, but a @%$()_ ain't one.

Replies are listed 'Best First'.
Re: system() status weirdness
by pc88mxer (Vicar) on Mar 28, 2008 at 18:18 UTC
    That's because Net::SSH::Expect is installing the following SIGCHLD handler: 
    sub reapChild {
   do {} while waitpid(-1,WNOHANG) > 0;
}

    [download]
    Doing this will give you your statuses back: 
    use Net::SSH::Expect;
...
$SIG{CHLD} = 'DEFAULT';
...
system(...);

    [download]
    I could be wrong, but I doubt the reapChild handler is absolutely necessary, so you're probably safe just use default handler even when you make Net::SSH::Expect calls.
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[select]
      This works great. Thanks alot ++.

      Bob

      I got 99 problems, but a @%$()_ ain't one.
[reply]

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