CLiki: detachtty

detachtty

detachtty is a Unix utility that lets you run interactive programs (such as Lisp) non-interactively. Also, it allows you to connect to them over the network when you do need to interact with them. It's intended for use with long-running server processes running in Common Lisp implementations.

If you've used screen, it's a similar concept, but more suited to traditional scrolling interfaces whereas screen is better for full-screen (e.g. curses-based) apps. Compared to screen, detachtty

has no capability to swap between different screens (doesn't eat C-a)
runs in line-at-a-time mode with no tty emulation (you can sanely use it in emacs comint modes or from inside a script(1) session)
has no features (less to go wrong)
and thus doesn't need a configuration file either

Example usage

server$ detachtty --dribble-file /var/log/cliki-dribble --log-file \
  /var/log/detachtty.log --pid-file /var/run/cliki.pid \
  /var/run/cliki-socket /usr/bin/lisp -eval '(load-system :telentweb)' \
  -eval '(progn (telentweb::init) (telentweb::start))' \

client$ attachtty dan@server:/var/run/cliki-socket

to quit attachtty press ^\

Running via detachtty at startup

Start a script late .. i.e. S9xlispapp in rc[2|3].d/

start S9xlispapp

#!/bin/sh
su - user -c /path/to/lisp-app-script

end S9xlispapp

start lisp-app-script

#!/bin/sh

detachtty --dribble-file /var/log/lisp-app-dribble --log-file \
  /var/log/detachtty.log --pid-file /var/run/lisp-app.pid \
  /var/run/lisp-app-socket /usr/bin/lisp -eval '(start-lisp-app)'

end lisp-app-script

-quasi (credit to Eduardo Muñoz for this information)

A more featureful init.d startup script for debian and compatible linuxes is introduced in https://boinkor.net/2006/02/starting-daemonized-lisp-images-in-debian/

Actual usage

detachtty is running the SBCL instance that CLiki runs on

Compatibility

detachtty is mostly tested on Debian GNU/Linux, but contributed patches for FreeBSD and Solaris have been merged into it, so it's probably not too hard to get running on many Unices

~~apparently, it worked on macos at one time, but that is no longer true under macos 10.4 (tiger). It seems that tiger's poll does not work as advertised.~~ it works on Tiger using poll-emulator from MacPorts ("OS_LOADLIBES=-lpoll -L/opt/local/lib" is the only change required to make it work on Intel, but I'm having some issues on PPC)

Download

i386 Debian and source packages (currently at version 9) are at ~~ftp://ftp.linux.org.uk/pub/lisp/detachtty/~~. This package is also available in the main Debian repository. There's also a FreeBSD port, misc/detachtty, which you can get from the ports tree.

A new version, which includes the ability to set timeouts and pass code to the detach'd lisp (for better scriptablity) is available in the darcs repo at:

~~http://common-lisp.net/project/bese/repos/detachtty~~

Patches against that code would are more than welcome.

Remark:

When I started my Lisp image at Systemstart I got always errors like:

c-string encoding error (:external-format :ASCII):
the character with code 195 cannot be encoded.
[Condition of type SB-INT:C-STRING-ENCODING-ERROR]

But it worked when I tried to start my Lisp image via the init.d script in the comandline.

The problem was solved when I added the following declarations to my init.d script:

LC_CTYPE=en_US.UTF-8
export LC_CTYPE