Date: Thu, 25 Sep 2008 09:40:54 +0200 From: Jonathan McKeown <jonathan+freebsd-questions@hst.org.za> To: freebsd-questions@freebsd.org Subject: Re: Netprint perl script from Handbook doesn't work Message-ID: <200809250940.54775.jonathan%2Bfreebsd-questions@hst.org.za> In-Reply-To: <20080924151235.GA3284@dan.emsphone.com> References: <3cc535c80809240333s1036386fnaa597267f0cf12aa@mail.gmail.com> <20080924151235.GA3284@dan.emsphone.com>
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On Wednesday 24 September 2008 17:12:36 Dan Nelson wrote:
> In the last episode (Sep 24), Andy Kosela said:
> > The netprint perl script provided in the Handbook (9.4.3.2) is not
> > working.. or am I missing something:
> >
> > plotinus:~> cat new.txt | lp.sh
> > Can't contact 10.10.21.12: Address family not supported by protocol
> > family at /usr/local/libexec/netprint line 21.
>
> Can you telnet to that ip address ("telnet 10.10.21.12 9100", or
> whatever port you're using)?
>
> > plotinus:> cat /usr/local/libexec/netprint
> > #!/usr/bin/perl
> > #
> > # netprint - Text filter for printer attached to network
> > # Installed in /usr/local/libexec/netprint
> > #
> > $#ARGV eq 1 || die "Usage: $0 <printer-hostname> <port-number>";
> >
> > $printer_host = $ARGV[0];
> > $printer_port = $ARGV[1];
> >
> > require 'sys/socket.ph';
> >
> > ($ignore, $ignore, $protocol) = getprotobyname('tcp');
> > ($ignore, $ignore, $ignore, $ignore, $address)
> > = gethostbyname($printer_host);
> >
> > $sockaddr = pack('S n a4 x8', &AF_INET, $printer_port, $address);
> >
> > socket(PRINTER, &PF_INET, &SOCK_STREAM, $protocol)
> >
> > || die "Can't create TCP/IP stream socket: $!";
> >
> > connect(PRINTER, $sockaddr) || die "Can't contact $printer_host: $!";
> > while (<STDIN>) { print PRINTER; }
> > exit 0;
>
> Wow. That's a really complicated way to say
>
> #! /bin/sh
> nc $1 $2
It's also ugly (and very old-fashioned) Perl. Starting at (and replacing) the
require 'sys/socket.ph' line (which is Perl 4, I think), it should look more
like this (with appropriate error-checking added):
use Socket;
my $proto = getprotobyname('tcp');
socket(my $socket, PF_INET, SOCK_STREAM, $proto);
my $sock_in = sockaddr_in($printer_port, inet_aton($printer_host));
connect($socket, $sock_in);
Although this rewrite removes the need, if you want in general to ignore some
of the return values of a function returning a list, the usual way is to
assign to undef:
(undef, undef, undef, undef, $address) = gethostbyname($printer_host);
Although when you're throwing away that many, it makes more sense to index the
returned list in the same way you would index an array:
$address = (gethostbyname($printer_host))[4] # returns 5th element
I really should submit a doc patch for this (incorporating Dan's sterling
suggestion of nc $1 $2).
Jonathan
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