lcmdx.c

lcmdx.c - send command to LISTSERV on remote node via TCPGUI interface

Official source: lcmdx.c in the Developers Guide for LISTSERV®, version 1.8e

A patched lcmdx.c is available that allows command line arguments to be safely passed via stdin. This prevents snooping eyes on the local system from seeing LISTSERV passwords and commands issued -- which can be seen by looking up command line args or environment in the public system process lists (e.g. with top).

[NB: the link between your machine and the LISTSERV machine is unencrypted and so your LISTSERV password and other private information is still travelling clear-text on the wire. You might set up an SSH tunnel between the machines to overcome that limitation.]

Example usage of patched lcmdx.c:

$ lcmdx - - - -
lists.example.com
devnull@example.com
devnull-LISTSERV-password
thanks
^D^D

#!/usr/bin/perl -Tw
$::ENV{'PATH'} = '/usr/local/bin:/bin:/usr/bin';
delete $::ENV{'BASH_ENV'};

use strict;
use IPC::Open3 ();

my $host    = 'lists.example.com';
my $email   = 'devnull@example.com';
my $pass    = 'devnull-LISTSERV-password';
my $command = 'thanks';

my($wtr,$rdr,$err);
my $pid = IPC::Open3::open3($wtr, $rdr, $err, 'lcmdx', '-', '-', '-', '-');
print $wtr join("\n", $host, $email, $pass, $command);
close $wtr;
print while (<$rdr>);

LCMDX.pm

The LCMDX.pm Perl module is a simple convenience library that wraps lcmdx, further building on the Perl code example above and employing the patched lcmdx.

For more information about the types of commands that you can send to LISTSERV, please see the current LSoft manuals