+++ /dev/null
-;;;;;
-title: Lisp layered on Unix
-tags: lisp,unix,emacs
-date: 2014-11-27 21:31:10
-format: md
-;;;;;
-
-[This blog post][heart] on LispCast is a pretty good start to get thinking
-about the intricacies of the interaction between Lisp (Machine) ideas and the
-current Unix environment. Of course that includes plan9 on the one side and
-Emacs on the other.
-
-[heart]: http://www.lispcast.com/the-heart-of-unix (The Heart of Unix)
-
-# Lisp shell
-
-There is [scsh](???), but it's not really what I'm looking for. Using emacs as
-login shell (with the `eshell` package) comes closest to it regarding both
-with existing commands and integration of Lisp-based ones. However, while
-pipes work as expected with `eshell`, data is still passed around as
-(formatted) text. There doesn't seem to be an easy way to pass around
-in-memory objects, at least while staying in Emacs itself. That would of
-course mean to reimplement some (larger?) parts of that system.
-
-This all ties in to the idea that unstructured text isn't the best idea to
-represent data between processes. Even though Unix pipes are extremely useful,
-the ecosystem of shell and C conventions means that the obvious way isn't
-completely correct, meaning that there are edge cases to consider. The best is
-something as innocent as `ls | wc -l`, which will break, depending on the shell
-settings, with some (unlikely) characters in filenames, i.e. newlines.
-
-#
-
-One of the problems is obviously that in order to pass around structured data,
-i.e. objects, all participants have to understand their format. Passing
-references won't work without OS support though.
-
-Instead of having unstructured streams, use streams of (data) objects. The
-distinction here is Plain Old Objects (PODs) instead of objects with an
-associated behaviour.
-
-Let's take a look at standard Unix command line tools (I'm using GNU Coreutils
-here) in order to reproduce the behaviour and/or intent behind them:
-
-## Output of entire files
-
-The first command here is `cat`. Although GNU `cat` includes additional
-transformations, this command concatenates files. Similar to the description,
-we can image a `CAT` to perform a similar operation on streams of objects.
-
-It doesn't make much sense to concatenate a HTML document and an MP3 file
-(hence you won't do it in most cases anyway). However, since files are
-unstructured, `cat` can work on them.
-
-# Registering functionality
-
-Although you can call commands individually on files, some of them form an
-ad-hoc service interface already: The C compiler, along with the toolchain
-forms one such interface, where you're required to use the same interface if
-you want to seamlessly replace one part of the toolchain.
-
-Same goes for the Coreutils: As long as you honour the interface, programs can
-be replaced with different implementations.
-
-# Interactive commands
-
-Emacs has a special form `interactive` to indicate whether a command can be
-directly called via the command prompt. There is also special handling there
-to accomodate the use of interactive arguments. This is something that can be
-generalised to the OS. An example of where this already happens is the
-`.mailcap` file and the `.desktop` files from desktop suites.
-
-# Threading and job control
-
-Unfortunately getting proper job control to work will be a bit of a problem in
-any Lisp implementation, since the best way to implement the concurrent jobs is
-using threads, which are not particularly suited for handling the multitude of
-signals and other problems associated with them. Even without job control
-pipelines implemented in Lisp require shared in-memory communication channels,
-so something like (object-based) streams, mailboxes, or queues are necessary to
-move IO between different threads.
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