triggers 0.41
-------------

This is beta level software.

Triggers is a generic service that allows programs to notify users about
events.  Programs activate triggers when something interesting happens
and users tie arbitrary behavior to them (run a program, play a sound)
as directed by a home directory config file; the interaction occuring
through an efficient daemon.  Triggers can be passed off to other hosts,
facilitating distributed actions.  Triggers are lightweight and asynchronous.

A simple, fast library call is available to add triggers to software.
Scripts can use an executable version.

?? Programs trying to initiate triggers always talk to a local daemon,
?? returning instantly to other tasks, even in failure.

The trigger daemon does not write anything to disk, but will reliably
transmit triggers while a machine is up; undeliverable triggers are
destroyed after 48 hours.

User root cannot receive triggers.

See section Setup for installation instructions.

Caveats
-------
Triggers are never stored to disk.  If your machine tanks, so do any extant
messages.

Faking a trigger is easy.

Failure of configuration files, hostnames, bogus users, etc., results in
a trigger's destruction.

Usage
-----

They must be strings without null bytes.


Internals
---------

triggerd is implemented with three threads.  The first (and highest priority)
manages locally generated triggers.  2 - socket server.  3 - outgoing
triggers.

triggerd keeps a small cache of most-used user trigger commands, to avoid
re-reading triggerrc files.

Protocol
--------

port 861.  picked at will.

This section is probably interesting only to bla...

version (1) + length/field pairs (user, service, action, data) (2/?) +
timestamp (8) + delay (4) + hops (4)


Following rules:

1. A server must discard triggers violating length restrictions.
2. A server must ... rounding on delay ... timestamping.
3. A trigger undeliverable for 24 hours must be discarded.
4. A server must initialize a trigger to one hop.

1. After 48 hours, a server may discard a trigger. [??]
2. ...

Ideas
-----

1. Be alerted to mail on a faraway server when you actually receive it,
instead of polling it every 5 minutes.  Combine this with real-time channel
mixing, and some ducking algorithms, and you can centralize audio cues.

2. Custom handle talkd. tcl/tk popup

3. bla


Setup
-----

 q) Depending on your version of libc, you might want to grab Tom ..'s latest
    regular expression package, prep.ai.mit.edu/Rx-1.1...,
        # follow his instructions :)

 r) If you're using libc prior to version 6, install LinuxThreads.
    ftp://ftp.inria.fr/INRIA/Projects/cristal/Xavier.Leroy/linuxthreads.tar.gz


Credits
-------

Thanks to Anders Brownworth for testing.

References
----------

1. http://www.evantide.com/~jeremyw/software.html
2. http://www.pobox.com/~djb

Finale
------

This package is released into the public domain.  Do with it what you will;
I'm not responsible in any way for its use.

Thoughts, criticism, patches and hate mail, welcome and appreciated.

April 22, 1998
Jeremy Wohl / jeremyw@evantide.com
http://www.evantide.com/~jeremyw/software