list_processes aka ps

This is part 3 in my occasional AnyEvent series

• First Steps with AnyEvent
• Emulating POSIX Signals
• List Processes AKA ps
• Bad AnyEvent Install

Now that we have our userspace kernel, it is time to write the utilities to make it more pleasant to use. On Linux, I can simulate all of the commands using telnet, but my Windows box doesn’t have telnet installed. I will therefore need a list_processes command, a signal command and a library to help with registering new processes.

First up is list_processes which is modelled on the http_get function presented in AnyEvent::Intro. It simply needs to send:

list_processes\015\012

and then call the passed in function with each line of response. The result might be something like the following.

$ ./list_processes.pl
1: ./register.pl a b c
2: ./register.pl

---

list_processes.pl

use 5.010;

use strict;
use warnings;

use constant DEBUG => $ENV{KERNEL_DEBUG};

my $cr = "\015\012";

use AnyEvent::Handle;

sub list_processes
{
    my ($host, $port, $cb) = @_;

    my $cv = AE::cv();

    my $handle; $handle = AnyEvent::Handle->new(
        connect  => [$host => $port],
        on_error => sub {
            say("Connection error: $!");
            $handle->destroy();
        },
        on_eof => sub {
            DEBUG && say 'Connection closed';
            $handle->destroy();
            $cv->send();
        }
    );

    $handle->push_write('list_processes' . ${cr});

    $handle->on_read(sub {
        my $handle = shift;
        my $data = $handle->rbuf();
        $handle->rbuf() = '';
        $data =~ tr/\r//d;
        foreach my $line (split /\n/, $data) {
            $cb->($line);
        }
    });

    return $cv;
}

my $cv = list_processes('localhost', 12345, sub { say @_ } );
$cv->recv();

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