Sorry about the indention... must be the mail client i'm using.
I need to fork because the external program I want to run inside the child runs
infinitely. I want to have a timer running in the parent and after that, kill
the child. Without forking, I have to do a pkill myprogname
I'm reading the perlipc now.. nothing so far..
--- On Wed, 5/27/09, Chas. Owens <chas.ow...@gmail.com> wrote:
> From: Chas. Owens <chas.ow...@gmail.com>
> Subject: Re: variables gets shared to child but resets back after exiting fork
> To: "Michael Alipio" <daem0n...@yahoo.com>
> Cc: "begginers perl.org" <beginners@perl.org>
> Date: Wednesday, May 27, 2009, 7:15 PM
> On Wed, May 27, 2009 at 05:42,
> Michael Alipio <daem0n...@yahoo.com>
> wrote:
> >
> > Hi,
> >
> > I have to run an external program but the program does
> not termination on some conditions, e.g, ping, will not exit
> unless you specify -c or some other circumstances.
> >
> >
> > Now I what I want to do is:
> >
> > my @array;
> > die "Cannot fork myprog" unless (defined my $pid =
> fork)
> > if ($pid==0){
> > open MYPROG, "myprog |" or die "Cant run myprog";
> > my $timeout = 0;
> > while (<MYPROG>){
> > exit(0) if $timeout == 3;
> > push @array, $_;
> > sleep 1;
> > $timeout++;
> > }
> >
> > waitpid($pid, 0);
> > print "@array\n";
> >
> >
> > The problem with the code above is that @array goes
> back to its initial state after exiting the child. No
> contents are printed. I even tried references but it didn't
> work as well.
> >
> > If I don't use fork, I the way I would kill the
> process is by doing a call to pkill. With fork, it would be
> much easier with exit. However the output of external
> program gets discarded.
> >
> > Can you think of any workaround for this?
> snip
>
>
> Variables are not shared between parent and child.
> The values of the
> parent's variables are copied to the child at the time of
> the fork.
> You really need to read perldoc perlipc[1]. And you
> need to learn how
> to indent code. Leaving your code all against the
> left side of the
> screen makes it hard to read.
>
> Of course, the biggest question is why are you bothering to
> fork in
> the first place? Why not just say
>
> my $program = "myprog";
>
> open my $pipe, "-|", $program
> or die "Cant run $program: $!";
>
> my @array;
> for (1 .. 3) {
> last unless defined(my $line =
> <$pipe>);
> push @array, $line;
> }
>
> close $pipe;
>
>
>
> 1. http://perldoc.perl.org/perlipc.html
>
> --
> Chas. Owens
> wonkden.net
> The most important skill a programmer can have is the
> ability to read.
>
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