I think Wheel Run is one of the best parts of POE for what I do!
Especially useful can be the coderef executions. With this example, you
should be able to do any of the following:
# in some routine in my session ...
$kernel->yield( 'run_something_async', "/usr/sbin/sendmail" );
# or
$kernel->yield( 'run_something_async', sub { print "I'm running in child
process $$ ! } );
# or
$kernel->yield( 'run_something_async' [ '/usr/local/bin/my_program',
'-a', $argument_1, '-b', $argument2 ] );
sub run_something_async {
my( $heap, $kernel, $what ) = @_[ HEAP, KERNEL, ARG0 ];
# this isn't necessary if you put the event in inline_states
# at POE::Session creation time
$kernel->state('my_input_event', \&handle_input_event );
$kernel->state('whine_about_error', \&error_handler );
# create a new wheel, storing a reference to it in my heap
$heap->{run_wheel} = POE::Wheel::Run->new(
Program => $what,
ErrorEvent => 'whine_about_error',
StdoutEvent => 'my_input_event',
StderrEvent => 'my_input_event', # or its own handler
Filter => POE::Filter::Line->new()
);
# send SOME DATA to the child process's STDIN
$heap->{run_wheel}->put( "SOME DATA" );
}
# this is input from the child process
sub handle_input_event {
my( $heap, $buffer, $wheel_id ) = @_[ HEAP, ARG0, ARG1 ];
print "I got this: '$buffer' from wheel $wheel_id\n";
# Send SOME MORE DATA to the child's standard in
$heap->{run_wheel}->put( "SOME MORE DATA" );
}
sub error_handler {
my($heap,$buffer,$error,$wheel_id) = @_[HEAP,ARG0,ARG1,ARG2];
# do something ...
}
-Al Tobey
Unix Administrator
On Thu, 2002-03-14 at 17:01, Ryan White wrote:
> I have tried a number of different things. Immediately after I sent my post
> I noticed the missing LF. I have added that and I still get no return value.
> Inline comments...
>
> From: "Rocco Caputo" <[EMAIL PROTECTED]>
> > On Thu, Mar 14, 2002 at 01:45:28AM -0800, Ryan White wrote:
> > > I am looking for an example using Wheel::Run within a child process. I
> need
> > > to know how to read the output of a Wheel after using put.
> [..]
> > >
> > > sub child_start {
> > > my ($kernel, $session, $parent, $heap, $email) = @_[KERNEL, SESSION,
> > > SENDER, HEAP, ARG0];
> > >
> > > # Remember the parent.
> > > $heap->{parent} = $parent;
> > >
> > > warn "Child ", $session->ID, " will validate $email.\n";
> > >
> > > # Check the passed email address.
> > >
> > > my $program = [ "./check_addr.pl" ];
> > > my $wheel = POE::Wheel::Run->new(
> > > Program => $program,
> > > StdoutEvent => &stdout, # Event to emit with child
> stdout
>
> I have also tried using 'stdout' but it never calls the stdout method..
> Where should the stdout method be defined. I had the following in my creat
> child function:
> sub create_a_child {
> my $email = shift;
> POE::Session->create
> ( inline_states =>
> { _start => \&child_start,
> _stop => \&child_stop,
> stdout => \&child_stdout,
> },
> args => [$email],
> );
> }
>
> Is this not the correct method? When I used this code it would never call te
> child_stdout method. Which session does it need to be in?
>
> [..]
> > > }
> >
> > I see two problems here:
> >
> > First, you are not storing the new POE::Wheel::Run instance in $heap,
> > so it's destructing as soon as child_start() returns.
>
> I didn't see anything in the POE::Wheel::Run docs about putting the instance
> in $heap. What is the convention for that
>
> > Second, your StdoutEvent should be an event name, not a code
> > reference.
> >
> > [...]
> >
> > > And the check_addr.pl program simply looks like this
> > > #!/usr/bin/perl
> > > my $email = <>;
> > > chomp($email);
> > > print 1;
> > >
> > > It doesn't seem to ever be able to read the data that check_addr sends
> back.
> > > Should I be doing this another way?
>
> Ok the script now looks like this
> #!/usr/bin/perl
> use strict;
> $| = 1;
> my $email = <>;
> chomp($email);
> print "1\n";
>
> I over simplified the script so that it only test the wheel processes. I am
> attaching the scripts so that you can see if I'm missing something easier.
> What I think it happening (not sure if it make sense) is the child it
> calling the wheel but has nothing else to do so it then exits before getting
> stdout.
>
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