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Hack 64 Welcome Visitors Automagically

figs/moderate.gif figs/hack64.gif

Create a simple bot that welcomes visitors to your IRC channels.

" Can I ask a question?" Users of busy channels will often observe newcomers popping in and asking this. You may wonder why they don't just ask their question, allowing people to choose whether or not to answer it, rather than having to answer the redundant question as well.

10.2.1 Channel Rules

Many IRC channels have a basic set of ground rules associated with them. The regular inhabitants of the channel generally know these rules and abide by them. A lot of rules are common sense and are put in place to avoid wasting people's time. Busy IRC channels invariably have lots of first-time visitors. Some of these visitors tend to be unaware of the rules, including the ones that you may consider to be common sense! Consider including the rules in a welcome message that is sent as soon as newcomers join the channel.

10.2.2 Welcome Options

Welcome messages can be sent to people who have just arrived in a channel in a number of ways. Sending a message to the entire channel is definitely one method to avoid, as only the newcomer will find the message relevantónobody else in the channel will want to keep seeing it again and again. Sending a private message to the newcomer is a better option, as it won't annoy other users. However, most clients display private messages in a different window or tab, so some people opt to send a notice to the user instead. Many clients display notices in the active window that are easily distinguished from normal messages.

Sometimes people aren't around to personally deliver welcome messages in a timely fashion, so a bot comes into play.

10.2.3 The Code joins multiple channels and uses a unique welcome message for each channel:

import org.jibble.pircbot.*;

import java.util.HashMap;

public class WelcomeBot extends PircBot {


    // This maps channel names to welcome messages.

    private HashMap welcomes = new HashMap( );

    private static final String defaultWelcome = "Welcome to this channel.";


    public WelcomeBot(String name) {




    // Adds a new welcome message to the bot.

    public void addWelcome(String channel, String welcome) {

        welcomes.put(channel.toLowerCase( ), welcome);



    // Returns a welcome message for the specified channel.

    private String getWelcome(String channel, String nickname) {

        String welcome = (String) welcomes.get(channel.toLowerCase( ));

        // If there is no welcome message for this channel, use the default.

        if (welcome == null) {

            welcome = defaultWelcome;


        // Replace $channel and $nickname if they are found.

        welcome = welcome.replaceAll("(?i:\\$channel)", channel);

        welcome = welcome.replaceAll("(?i:\\$nickname)", nickname);

        return welcome;



    // This method gets called whenever someone joins a channel.

    public void onJoin(String channel, String sender,

            String login, String hostname) {


        if (!sender.equalsIgnoreCase(getNick( ))) {

            // Send a welcome notice to the visitor.

            sendNotice(sender, getWelcome(channel, sender));




The bot will welcome users to all of the channels into which it has been sent. In your main method, you can add specific welcome messages for each channel. If you do not specify these, the default welcome message will be used.

Set a custom welcome message for a channel by calling the addWelcome method:

bot.addWelcome("#channel", "Welcome to our channel... behave nicely!");

Your welcome message can also make use of the $channel and $nickname variables, which will be automatically replaced by the bot, for example:

bot.addWelcome("#channel", "Welcome to $channel, $nickname.");

Create a file called . You will use this to specify your welcome messages and tell the bot which channels to join:

public class WelcomeBotMain {


    public static void main(String[] args) throws Exception {

        WelcomeBot bot = new WelcomeBot("WelcomeBot");



        bot.addWelcome("#irchacks", "Welcome to $channel, $nickname");








10.2.4 Running the Hack

Compile the bot like so:

C:\java\NntpBot> javac -classpath .;pircbot.jar *.java

You can then run the bot by entering:

C:\java\NntpBot> java -classpath .;pircbot.jar WelcomeBotMain

10.2.5 The Results

Figure 10-1 shows the WelcomeBot in action, delivering welcome notices to two channels. In the top half, you can see the default welcome notice being sent as I join the channel #test. In the bottom half, you can see the custom welcome notice that was specified in

Figure 10-1. WelcomeBot delivering welcome notices to two channels

If your IRC network runs a ChanServ service, an alternative approach is to use ChanServ [Hack #9] to send welcome notices to users.

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