Scsh 0.5.2 Release notes -*- outline -*- We are pleased to release scsh version 0.5.2. The new release has many bug fixes, improvements and new features. The text below gives a general description of scsh, instructions for obtaining it, pointers to discussion forums, and a description of the new features in release 0.5.2. (Emacs should display this document is in outline mode. Say c-h m for instructions on how to move through it by sections (e.g., c-c c-n, c-c c-p).) This release is the first new release of scsh in over a year. We've been using it, and have had no problems. However, we only recommend eager users download it. We'll upgrade it to a 0.5.3 release after a week or two, when this release has been shaken out. * What is scsh ============== Scsh is a broad-spectrum systems-programming environment for Unix embedded in R4RS Scheme. ** Scsh as a scripting language ------------------------------- Scsh has a high-level process notation for doing shell-script like tasks: running programs, establishing pipelines and I/O redirection. For example, the shell pipeline gunzip < paper.tex.gz | detex | spell | lpr -Ppulp & would be written in scsh as (& (| (gunzip) (detex) (spell) (lpr -Ppulp)) ; Background a pipeline (< paper.tex.gz)) ; with this redirection Scsh embeds this process notation within a full Scheme implementation. The process notation is realized as a set of macro definitions, and is carefully designed to allow full integration with standard Scheme code. Scsh isn't Scheme-like; it is Scheme. At the scripting level, scsh also has an Awk design, also implemented as a macro that can be embedded inside general Scheme code. Scripts can be written as standalone Scheme source files, with a leading #!/usr/local/bin/scsh -s trigger line. ** Scsh as a systems-programming language ----------------------------------------- Scsh additionally provides the low-level access to the operating system normally associated with C. The current release provides full access to Posix, plus important non-Posix extensions, such as complete sockets support. "Complete Posix" means: fork, exec & wait, sockets, full read, write, open & close, seek & tell, complete file-system access, including stat, chmod/chgrp/chown, symlink, FIFO & directory access, tty & pty support, file locking, pipes, select, file-name pattern-matching, time & date, environment variables, signal handlers, and more. In brief, you can now write Unix systems programs in Scheme instead of C. For example, we have implemented an extensible HTTP server at MIT entirely in scsh. As important as full access to the OS is the manner in which it is provided. Scsh integrates the OS support into Scheme in a manner which respects the general structure of the language. The details of the design are discussed in a joint MIT Lab for Computer Science/University of Hong Kong technical report, "A Scheme Shell," also to appear in a revised format in the *Journal of Lisp and Symbolic Computation." This paper is also available by ftp: ftp://ftp-swiss.ai.mit.edu/pub/su/scsh/scsh-paper.ps ** Scsh is a portable programming environment --------------------------------------------- Scsh is designed for portability. It is implemented on top of Scheme 48, a byte-code-interpreter Scheme implementation. The Scheme 48 virtual machine can be compiled on any system with a C compiler; the rest of Scheme 48 is machine-independent across 32-bit processors. Scsh's OS interface is also quite portable, providing a consistent interface across different Unix platforms. We currently have scsh implementations for: AIX BSD/OS CXUX FreeBSD HP-UX IRIX Linux NetBSD NeXTStep Solaris SunOS Ultrix Win32 Scsh code should run without change across these systems. Porting to new platforms is usually not difficult. * Obtaining and installing scsh =============================== You can get a copy of scsh via anonymous ftp, from ftp://ftp-swiss.ai.mit.edu/pub/su/scsh/scsh.tar.gz The tar file includes a detailed manual and a paper describing the design of the system. For the lazily curious, we also have the manual separately available as ftp://ftp-swiss.ai.mit.edu/pub/su/scsh/scsh-manual.ps Just click 'n view. You *should* be able to build scsh on the standard platforms with exactly five commands: gunzip, tar, cd, ./configure, and make. The configure script figures out the special flags and switches needed to make the build work (thanks to the GNU project for the autoconfig tool that makes this possible). After doing the make, you can start up a Scheme shell and try it out by saying ./scshvm -o ./scshvm -i ./scsh/scsh.image See the manual for full details on the command-line switches. If it's harder than this, and your system is standard, we'd like to know about it. * Getting in touch ================== There are two main ways to join in scsh-related discussion: the mailing-list scsh@zurich.ai.mit.edu and the netnews group comp.lang.scheme.scsh These two forums are exactly equivalent, being bi-directionally gatewayed at MIT. Bugs can be reported to scsh-bugs@zurich.ai.mit.edu If you do not receive the alt netnews hierarchy, or wish to join the mailing list for other reasons, send mail to scsh-request@zurich.ai.mit.edu * The World-Wide What? ====================== We even have one of those URL things: http://www-swiss.ai.mit.edu/scsh/ * New in this release ===================== ** Scsh is now "open source." We finally got around to tacking an ideologically hip copyright onto the source. (Not that we ever cared before what you did with the system...) The Scheme 48 authors have also graciously retrofitted a BSD-style open-source copyright onto the underlying Scheme 48 0.36 platform for us. The whole system is now open source, top-to-bottom. Take all the code you like; we'll just write more. ** CVS repository will be public-readable We will add further information to the web-site as soon as possible. ** New char-sets and char-set operations See the manual for more information on using character sets for text processing. Also, see the ccp package in scsh/scsh/lib for a new library providing character->character partial maps, which are also useful for general string processing. ** New regular expression system There's a whole, new regexp package in scsh. There's a new, s-expression-based notation for regexps, called SRE's. The new notation has been integrated into the AWK macro and field-parser functions. The older Posix notation is still supported for backwards compatibility. There's a whole chapter on regexps in the new manual; it has full details. The previous AWK and field-reader system is provided in a backwards-compatibility package. See package obsolete-awk-package in scsh-package.scm. ** New libraries The SRFI-1 list library is available, in the list-lib package. There is a large, powerful string-processing library available in the string-lib package. See the directory scsh/scsh/lib/ for documentation and source. These libraries make basic list and string hacking very straightforward. ** Renaming We are shifting from a reduce-foo convention to a more standard foo-fold convention. This has caused the following renamings: reduce-char-set => char-set-fold reduce-port => port-fold The older names are still bound, but are deprecated and will likely go away in a future release. String utilities INDEX and RINDEX are gone. Use the string-lib procedures instead. ** Bugfixes Over a year's worth of bug fixes. In particular, the old problems with the signal system blowing up builds on some of the more obscure Unix systems have been fixed. * Thanks ======== We would like to thank the members of local-resistance cells for the Underground everywhere for bug reports, bug fixes, design review and comments that were incorporated into this release. We really appreciate their help, particularly in the task of porting scsh to new platforms. Alan Bawden Jim Blandy Per Bothner Tom Breton Christopher Browne Sean Doran Ray Dillinger Allyn Dimock Scott Draves Lutz Euler Kevin Esler Jeremy Fitzhardinge Noah Friedman Martin Gasbichler Andy Gaynor Ian Grant Eric Hanchrow Karl Hegbloom Johann Hibschman Ian Horswill & the Northwestern Scheme wizards Gary Houston Graham Hughes Jarmo Hurri Lars Kellogg-Stedman Andre Koehoerst Shriram Krishnamurthi Jakob Lichtenberg Eric Marsden Peter C. Olsen Willliam Pippin David Rush Michael Schinz Manuel Serrano Mark Shirle Bill Somerfeld Mike Sperber Harvey J. Stein Pawel Turnau Rob Warnock Kenneth R. Westerback We'd like to thank everyone else for their patience; this release seemed like a long time coming. Brought to you by the Scheme Underground. Go forth and write elegant systems programs. -Olin Shivers, Brian Carlstrom & Martin Gasbichler Cambridge 29 September 1999