simple beginners problem

[neal83]

i am trying to teach myself perl and network programming with perl and i am unsure of what the problem is with the following code:

#!/usr/local/bin/perl
print "PID=$$\n";
my $child = fork();
die "cant fork: $!" unless defined $child;
if ($child > 0){ #parent process
print "parent process: PID=$$, child= $child\n";
}
else{ #child process
my $ppid = getppid();
print "child process: PID= $$, parent= $ppid\n";
}

i know its not much but the code is copied fom a book, the thing is it should work and its giving me a headache. i have windows XP pro and running perl 5.6

thanx in advance

 

[jrig]

It would be helpful if you posted what specific error you are getting.

The code as posted works so I'm guessing your path-to-perl line is wrong-->#!/usr/local/bin/perl
Sorry, I'm not sure what it is for windows, but a quick google should help-

 

[travs69]

Perl forking in windows is a bit of a pain. I find it easier to use the Parallel Fork Manager module. I can fork in unix no problem but windows always gave me fits.

 

[KevinADC]

The code as posted works so I'm guessing your path-to-perl line is wrong-->#!/usr/local/bin/perl

For future reference, Windows ignores the shebang line. But you are correct it is wrong for a Windows environmnt, but unless this is a CGI script, it won't matter.

Windows shebang line is generally:

#!c:\perl\bin\perl.exe

or:

#!perl

------------------------------------------
- Kevin, perl coder unexceptional!

 

[neal83]

sorry should be more specific, when i run the program in dos i get this:
PID=3067 #the id of the current process
the get getppid function is unimplemented at c:\perl programs\fork.pl line 9.

what i find a mystery (even when i use #!c:\perl\bin\perl.exe) is that it recognises the current process id in $$ yet it fails to fork() or recognise the getppid function, i think that since its working fine on your OS i might want to up date my version of perl to 5.8 but i thought that there would be support for fork() in windows, which their probably is but i will get it anyway.

thanx to those who tried it out, i hope someone can figure out why that wont run in windows though.

 

[stevexff]

Any reason you're running 5.6 and not 5.8.n ? 5.8 is hardly bleeding edge these days, and it might be fixed in the latest release...

Steve

[small]"Every program can be reduced by one instruction, and every program has at least one bug. Therefore, any program can be reduced to one instruction which doesn't work." (Object:erlDesignPatterns)[/small]

 

[travs69]

I am running 5.8 on XP

print "PID=$$\n";
my $pid = fork();

if ($pid){ 
   print "parent process: $pid\n";
}
else{ 
     print "child process: $pid\n";
}

This seems to work.. but $$ never matches the parent pid.. but I don't think it will in windows. Read the perlfork documentation in activestate.