# $EPIC: on,v 1.5 2001/01/08 16:25:07 jsb Exp $
Synopsis:
   on [<modes>]<hook> [<serial#>] [-|^]<match> [{ <action> }]

Description:
   The ON command is what truly gives ircII-EPIC its versatility.  It sets
   a hook that allows any arbitrary type of message be acted upon.  This
   allows for a high degree of automation with the client, as well as a
   high degree of customization.

   Each hook can have a set of modes associated with it.  There are 5
   (five) types of modes, and each one has a specific, unique purpose.  The
   hook name is prefixed with these modes.  The first 4 (four) control
   the output of the hook.

     +   The noisy mode.  This causes the client to display everything
         | the hook is doing.  It will display what event has been hooked,
         | and by what specific data.  This mode is really only useful for
         | script debugging.
     -   The quiet hook.  This suppresses display of the gory details of
         | the event hooked.
     ^   The silent mode.  This works similarly to '-', except it will
         | completely suppress the default output of the event.  Only ECHO
         | (and XECHO) will cause it to display anything.  This is most
         | often used to redefine how an event message looks.
    ?    The ambiguous mode.  This mode is special because the override level
         | is not determined when the on is registered, but is determined
         | separately each time the on is executed.  When you use this noise
         | level, the "noise" level is always the same as the SILENT level
         | (as if you had used '^'), but it will not automatically suppress the
         | client's default action as using '^' would.  The action of the on is
         | taken as an anonymous function: it may return a value with the
         | /return command.  If the return value of the action is 1 (one), then
         | the default action WILL be suppressed (as though you had used ^),
         | but if the return value is 0 (zero) then the default action will NOT
         | be suppressed (as though you had used -).

   Only one of the above four modes may be used per hook.  If none are
   used, the client defaults to a setting somewhere between noisy and quiet.
   It will display what it has hooked, but nothing else unless specifically
   coded to do so.

     #   The serial hook.  This allows the given hook to be assigned a
         | unique serial number (see Synopsis).  Thus, if multiple hooks of
         | the same type are defined, the order in which they are triggered
         | can be defined.  Refer to Serial_Numbers for more information.

   Each of the above sets of modes may be combined with the others (though
   only one from each set may be used per hook).

   The text matched for the hook is also rather versatile.  In the match
   string, any wildcard may be used.  The match must be surrounded by
   quotation marks (unless it is a single word).  If double quotes (") are
   used, the match string is evaluated when the hook is defined.  If single
   quotes (') are used, the match string is taken literally and evaluated
   each time the event is hooked.  This allows for variable matches to be
   used.  Additionally, the match string may be prepended with its own
   mode.

     -   This isn't really a mode, per se.  Rather, it is used to remove
         | any hook with the same match string.  If no match string is
         | given, all hooks for th given event are removed.
     ^   The exclusion mode.  This causes the client to do nothing when
         | the hook is triggered with the given match.  It is effectively
         | the same as only using a COMMENT in the action, or some other
         | noop command.

   The last part of a hook is the action.  This defines what the client is
   supposed to do when a hook is triggered.  The action can be just about
   anything the user wishes.  The syntax works basically the same as with
   ALIAS.  Braces are only required for multiline actions.  Also, as with
   aliases, hook actions can receive and use numeric expandos (representing
   the full event arguments hooked).

   Also, if this command is given with either none or a single argument, it
   will list all currently defined hooks matching the argument.

Examples:
   To redefine the default JOIN message:
      on ^join "*" {
         echo B*>*B $0 \($2\) has joined $1 [$Z]
      }

   To suppress channel messages from users from certain sites:
      assign ignore_em *@*.msn.com *@*.aol.com *@*.goodnet.com
      on -join ^'% % $ignore_em'

   To remove all hooks for a particular event:
      on join -

   To show an additional message for a certain site, after the default:
      on #-join 10 "% #blah %" {
         echo V***V Oh great, yet another person has joined $1
      }

See Also:
   Etiquette(7); Expressions(7); Programming(7); Serial_Numbers(7);
   Server_Numerics(7); Security(7); alias(5); echo(5); hook(5); 
   xecho(5);

Other Notes:
   ON allows for a great deal of automation of client activities.  This can
   be a bad thing if abused.  For instance, using it to automatically send
   a greeting to anyone joining a channel is usually considered bad form.
   Let common sense dictate when an automated response is appropriate.

