Eval-bot

An IRC bot for Common Lisp code evaluation

Introduction

Eval-bot is an Internet Relay Chat (IRC) robot program (a bot) which aims to help discussions related to the Common Lisp language. The bot sits on an IRC channel and can evaluate Common Lisp expressions and send their return value to IRC channel or user.

The bot program is implemented in the Common Lisp language. It must be used with an implementation that supports threads through Bordeaux Threads library. Minor parts in the bot's start and setting scripts use features specific to SBCL implementation.

IRC

Common Lisp package EVAL-BOT contains the IRC part of the program. Function make-client creates a client object which can be used with IRC-related functions, such as irc-connect, irc-join, irc-quit etc. Here is an example on how to run the bot.

1. Start the bot from shell.

   $ ./start-bot-sbcl
   

2. Use SBCL's REPL from the terminal or connect to the Swank server with Emacs's Slime.

   M-x slime-connect RET 127.0.0.1 RET 50000 RET
   

   If you use Slime you probably want to see bot's messages in the Slime buffer. Bot's message stream can be changed with variable eval-bot::*local-stream*. Write this in the Slime REPL buffer:

   (setf eval-bot::*local-stream* *standard-output*)
   

3. Switch to the EVAL-BOT package.

   (in-package #:eval-bot)
   

4. Create a client object for connections.

   (defparameter *client*
     (make-client :server "some.server.org"
                  :nickname "eval-bot"
                  :username "eval-bot"
                  :realname "Common Lisp Eval Bot"
                  :listen-targets '("#mychannel")
                  :auto-join '("#mychannel")))
   

   There is *freenode* client already. If you choose to use it, you may just change some of the slots:

   (setf (nickname *freenode*) "eval-bot")
   (push "#mychannel" (listen-targets *freenode*))
   (push "#mychannel" (auto-join *freenode*))
   

5. Connect.

   (irc-connect *client*)
   

   The bot will connect and automatically join to #mychannel. You can also use (irc-join client channel &optional password) function. Functions with irc- prefix are the IRC commands for the server. Raw IRC protocol commands can be sent with (irc-raw client raw-message).

6. Use the bot!

   <somenick> ,(values 1 2 3)
   <eval-bot> => 1, 2, 3
   <somenick> ,help
   <eval-bot> [bot prints information]
   

   Comma , is the default prefix for code evaluation. It can be changed with variable *eval-prefix*. Not all Common Lisp's features are supported. See the Sandbox section below.

If you want to make the startup process automatic you could create a Lisp file for your commands and start the bot with ./start-bot-sbcl --load mysettings.lisp.

Sandbox

Common Lisp expressions from IRC channels are evaluated in a restricted sandbox environment which provides a subset of Common Lisp's features. In general, many features related to symbols, packages and operating system have been disabled. Some standard functions and macros have been replaced with safer versions. The sandbox is implemented in packages SANDBOX-IMPL, SANDBOX-CL and SANDBOX-EXTRA. Function sandbox-impl:repl is the interface for sandbox code evaluation.

A single eval message from IRC results in a single answer message from the bot. Each IRC user has automatically her own sandbox package. So user-defined variables and functions are not shared between users. Users have their own REPL variables too: * ** *** / // /// + ++ +++. The user-specific sandbox package is temporary and is automatically deleted if not used for a while.

The source code

GitHub repository: https://github.com/tlikonen/cl-eval-bot

Copyright and license

Copyright (C) 2012-2016 Teemu Likonen <tlikonen@iki.fi>

OpenPGP key: 6965F03973F0D4CA22B9410F0F2CAE0E07608462

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

The license text: http://www.gnu.org/licenses/agpl.html