Re: fork issue in OVMS perl script

On Oct 12, 2009, at 5:23 AM, purnima bhandari wrote:

> Hi,
> I am new to OpenVMS Perl. I know that fork is currently not supported
> in the OVMS Perl (perl 5.8.6 on Ia64, VMS 8.3). I am currently trying
> to port the Perl script which has fork call and running successfully
> in UNIX environment. I saw in the readme documentation that we can use
> the vfork/exec instead. But I don't know how to use those in the Perl
> script and it is failing with below error.
>
> Below is the script snippet.
>
>
> Code snippet:
>
>
>  outln("($$) run_service()");
>  $log->debugln("($$) enter run_service()");
>
> # $pid = fork();  // Original script replaced with vfork below
>
>  $pid = vfork();
>  if($pid == 0) {         # we are the child
>    $SIG{CHLD} = $old_sigchld_hnd;
>    $SIG{INT}  = $old_sigint_hnd;
>
>
>
>
> The error:
>
> (574622047) enter run_service()run_observice calling vfork
> Undefined subroutine &main::vfork called at /opt/ovt/bin/ovt.pl line  
> 356.
> %SYSTEM-F-ABORT, abort
>
>
> Please guide me, where I am going wrong?
>

Not sure what the README in 5.8.6 says (that's a five-year-old release  
of Perl), but currently in perlvms.pod we say:

=item fork

While in principle the C<fork> operator could be implemented via
(and with the same rather severe limitations as) the CRTL C<vfork()>
routine, and while some internal support to do just that is in
place, the implementation has never been completed, making C<fork>
currently unavailable.  A true kernel C<fork()> is expected in a
future version of VMS, and the pseudo-fork based on interpreter
threads may be available in a future version of Perl on VMS (see
L<perlfork>).  In the meantime, use C<system>, backticks, or piped
filehandles to create subprocesses.

---

where the language indicates a bit better that the reference to vfork  
is not a reference to a Perl function but rather to the CRTL basis  
upon which a fork() in Perl could be (but isn't) implemented.  The  
last sentence is the important one: use system, backticks, or piped  
filehandles.  I'll just add that you may also want to look on CPAN for  
modules in the IPC::* namespace where there are some convenient  
abstractions that have had some effort to work portably.

________________________________________
Craig A. Berry
mailto:[email protected]

"... getting out of a sonnet is much more
  difficult than getting in."
                  Brad Leithauser