scheme shell

We are pleased to release scsh version 0.6.6. The main focus of this
release is support for the upcoming packaging proposal and the removal
of any code which did not conform to scsh's BSD-style license. In
addition, some bugs have been fixed.

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 0.6.6.  (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).)

* Contents
What is scsh
  Scsh as a scripting language
  Scsh as a systems-programming language
  Scsh is a portable programming environment
Obtaining and installing scsh
Getting in touch
The World-Wide What?
New in this release
 Removed or replaced non-free code
 New code for sorting
 Separate documentation of the library directories search facility
 New module CONFIGURE
 Argument processing more robust
 Ultrix is no longer supported
 Bug fixes
New in 0.6.5
New in 0.6.4
New in 0.6.3
New in 0.6.2
New in 0.6.1
New in 0.6.0

* What is scsh
Scsh is a broad-spectrum systems-programming environment for Unix embedded
in R5RS Scheme. It has an open-source copyright, and runs on most major
Unix systems.

** 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 
syof Lisp and Symbolic Computation."  This paper is also available by http:

** 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:
    Darwin/Mac OS X
    GNU Hurd

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
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
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
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

Currently, there is a mailing-list which is mirrored to a newsgroup.

To (un)subscribe to the mailing-list, send a message to  To submit a message to the
mailing-list, send it to

The mailing-list is also readable as a standard newsgroup, thanks to
gmane, a mail-to-news gateway. More information is available at the
following URL:

There used to be a newsgroup dedicated to scsh, called
comp.lang.scheme.scsh but it is now deprecated.

Bugs can be reported to
or via the Scsh project's bugs section on SourceForge:

* The World-Wide What?
We even have one of those dot-com cyberweb things:
We manage the project using SourceForge:

* New in this release

** Removed or replaced non-free code
   Some files in the previous versions of scsh did not conform to
   scsh's BSD-style license. We therefore removed the directory
   scheme/infix and asked the copyright holders of the rest of the
   code to put their code under a compatible license. The code of the
   sort package has been replaced by a new version (see below).

** New code for sorting
   The old package SORT from Scheme 48 has been replaced by a
   sophisticated library written by Olin Shivers for the withdrawn
   SRFI 32.

** Separate documentation of the library directories search facility
   The manual now contains a separate section that describes the
   library directories search facility. The description of the
   respective switches has been adapted accordingly.

** New module CONFIGURE
   The new module CONFIGURE permits access to some of the values
   obtained during the run of the configure script.

** Argument processing more robust
   Any number of whitespaces may now occur between the arguments to
   the VM.

** Ultrix is no longer supported
   The Ultrix platform is lacking support for POSIX regular
   expressions and is therefore no longer supported.

** Bug fixes
   Fix WITH-LOCk
   Ensure that the exit value is 1 if scsh exits due to an error
   Load the package scheme-with-scsh before dumping images to get
   better start-up times
   Fix two bugs in GLOB related to quotation
   The optmizer AUTO-INTEGRATE can now inline procedures with
   macro-generated arguments
   The optmizer FLAT-ENVIRONMENTS now works if invoked after AUTO-INTEGRATE
   Fixed a bug in the parser of "-" sre forms
   Removed accidentally committed expansion of paths in SCSH_LIB_DIR
   Fix the various SELECT-like procedures for 0 timeouts
   Let PATH-LIST->FILE-NAME return "/" for '("").
   Fix bug in S48_RECORD_TYPE: third parameter to s48_stob_ref was missing.
   Fixed check for -rdynamic   
   FIELD-READER returns (values EOF '()) on an empty port

* New in 0.6.5

** New platform: GNU Hurd
   Andreas Vögele ported scsh to GNU Hurd.

** ./configure option to set default scsh library directories 
   The ./configure script now accepts the option --with-lib-dirs-list
   to specify a list of default scsh library directories. In
   previous versions of scsh this list was hardwired to

** Support for DESTDIR for easier packaging
   The install target of the Makefile now respects the environment
   variable DESTDIR to allow package maintainers to use a staging

** New SRFI
   This release adds support for SRFI 42.

** Switch to load exec scripts from library path
   The new switch -lel searches the library path for a file and loads
   the file into the exec package.

** Removed scheme/infix/
   The directory scheme/infix/ had a non-free copyright licence and
   has been removed.

** Bug fixes
   - SEEK currently works on unbuffered ports only. Check this in the
     implementation and oopsify it in the manual.
   - Adjust documentation of some low-level regexp procedures
   - Removed message argument form errno-error
   - After fork/pipe, make the ports returned by the pipe the
   - Get the names of MAKE-STRING-PORT-FILTER and
   MAKE-CHAR-PORT-FILTER right in the doc
   - Fixed memory leak in scheme_cwd
   - Fixed memory leak in format_date
   - Avoid calling SOCKET-OPTION twice in case of an error
   - Fix for (rx (|)) by Peter Wang
   - Fix for (posix-string->regexp "$") by Peter Wang
** API changes
   None known.

* New in 0.6.4

** Switches to load exec scripts
   The new switch -le loads a file into the exec package, the new
   switch -de loads the "-s" script into the exec package.

** New SRFIs
   This release adds support for SRFI 25, 26, 27, 28 and 30.

** Bug fixes
   - Other select bug
   - Timeout for select is in seconds, not milliseconds
   - Load package md5 before dumping scsh.image
   - Revised implementation of SRFI-19
   - -sfd switch called bogus procedures
   - Ooopsify write-string/partial   
   - Clean up get_groups
   - Check for "." in file-name-{sans-}extension
   - Bug fix for let-match: variables may be #f
   - Fix some problems with WAIT-FOR-CHANNELS
   - Fixes in the time zone code
   - Fix a bug in SEND-MESSAGE: There is such a thing as an empty datagram
   - Renamed string-filter to make-string-port-filter and char-filter to

** API changes
   pause-until-interrupt has been removed because it is not compatible
   with the thread system

* New in 0.6.3

** Shorter startup times
   By a couple of small fixes we could diminish the startup
   time by 10-30%.

** stripped-scsh.image
   In addition to the standard heap image scsh.image, scsh now ships
   with an additional image stripped-scsh.image. This image contains
   the same code as the standard image but has almost all debugging
   information removed. It is therefore much smaller (2.5 MB vs. 4.5
   MB) which also allows shorter startup times. The image is intended
   for use in scripts but not for interactive development. See the
   manual for more information.

** MD5 support
   The package md5 contains a bunch of procedures to compute MD5

** New SRFIs
   This release adds support for SRFI 25, 26, 27, 28 and 30.

** API changes
   select and select! are supported again.
   Note however, that we recommend to use the new select-ports and
   select-port-channels procedures instead whenever possible.
   New interface to the uname function.
   New direct interface to the directory stream operations
   New structure scheme-with-scsh which combines the exports of the
     modules scsh and scheme, avoiding duplicates
   New procdures to work directly on file-info records
   The repl procedure has been removed
   New procedures connect-socket-no-wait, connect-socket-successful?
   Add lookup-external from recent S48

** Bugfixes
   LET-MATCH, IF-MATCH, and COND-MATCH now behave according to the
   Many bug fixes for the SRE system, specifically for dynamic
   PORT->SOCKET uses dups both ports of the socket
   Added missing process resource alignments
   No reaping for stopped children
   Initialize t.c_lflag before reading it.
   Fix to allow single character here strings.
   Add a whole bunch of S48_GC_PROTECT against s48_extract_integer.
   Added MAP, FOR-EACH, MEMBER, ASSOC to SRFI 1 interface
   Fixed a subtle bug in the macro for the << redirection
   Use "compare" und "rename" to compare symbols in lots of macros
   Fixed the close method for string-input-ports
   ... and many others.

* New in 0.6.2

** SRFIs
   In addition to SRFIs 1, 8, 13, 14 and 23 scsh now features SRFIs 2,
   5, 6, 7, 9, 11, 16, 17 and 19. See for a
   detailed description. The SRFIs are available in packages srfi-N
   where N is the number of the SRFI.

** port->socket
   New procedure port->socket to turn a port into a socket object was
   added to the network code.

** New forms in the module language
   The module language supports the new forms modify, subset and
   with-prefix from Scheme 48 version 0.57.

** API changes
   Fork, fork/pipe, fork/pipe+ take an optional argument
   continue-threads? to determine whether all threads should continue
   to run in the child.

   exec-path-list is now a preseved thread fluid

** PDF version of the manual
   There is now a PDF version of the manual generated by pdflatex.

** Bugfixes
   - Added default argument to tty-info as described in the manual
   - Conversion to s48_value in tty1.c
   - Fixed another hygiene problem in SRE
   - Plugged space leak in bind-listen-accept-loop
   - Aligned CWD and umask in various file operations
   - Better releasing of port locks
   - Corrected exception of time
   - Set-cloexec to #t for unrevealed ports.
   - Included scsh paper in the distribution.
   - Fixed accept for AF_UNIX
   - (setenv var #f) now deletes var from environment
   - Quoted { and } within literal strings of regexps

* New in 0.6.1

** API changes
  For sre's, BOW, EOW, WORD, and WORD+ (which were already unsupported
  in 0.6.0 on most platforms) are gone for good.

** Bugfixes
  Most of the known bugs of version 0.6.0 have been fixed, many thanks for
  the precise reports! See the project page on SourceForge for a list
  of the remaining known bugs. Here is a brief overview of the fixes:

  - GC_PROTECT'ed the necessary variables (specifically, where >1 arg to
    a function 'may GC') (Thanks to Steven Jenkins for dealing with this)
  - Fixed various race conditons in the signal handling and process reaping code
  - Fixed bug in set-process-group
  - If $HOME is unset, consult (user-info (user-uid)) for the value of 
  - Fix external-call-from-callback problem leading to spurious
        gc-protection-mismatch exceptions.
  - Let s48-do-gc return 0 so the PreScheme compiler will emit the correct
        signature of the function.
  - scsh/linux/tty-consts.scm: num-ttychars seems to be 32 not 19.
  - scsh/top.scm: Return 0 exit status for -c and -e.
  - *.c: Replaced // comments.
  - scsh/syslog1.c: Remove LOG_LPR from list of syslog levels.
  - scsh/network1.c: Pass SYSCALL argument to ERRNO-ERROR.
  - scsh/syscalls1.c: Disable timer interrupts before execve
  - scsh/network.scm: Correct name extraction in bind-socket
  - Added export for with-error-output-port
  - Install HTML version of manual under $(libdir)
  - ./configure is more rebost wrt $(srcdir)
  - Fixed installation of the S48 manual
  - Replaced several /tmp by /var/tmp 
  - Catch EISDIR in delete-filesys-object
  - flush-all-ports is now non-blocking

* New in 0.6.0

** Scsh is now based on Scheme 48 0.53  
  With the move from Scheme 48 version 0.36 to version 0.53 in this
  release the underlying system received a massive update. The most
  significant changes include:
    User level threads
    Advanced garbage collector
    Improved foreign function interface to C

  The most significant change for Scsh users is the addition of a
  user-level thread system. Scsh provides various features to deal
  with this new power in a system programming environment: An event
  based interface to interrupts, thread local process state and
  thread-safe system calls.

** A manual for Scheme 48 has been included
  Richard Kelsey, the author of Scheme 48, has graciously allowed us
  to retrofit the current Scheme 48 manual for inclusion in this scsh

** Interfaces to dot-locking, crypt and syslog
  Scsh now provides advisory file locking via the dot-locking scheme
  and a direct binding to the crypt function. Furthermore we added
  a complete, system-independent and thread-safe interface to syslog.

** API changes
  Some features of the previous releases are currently not
  supported as we did not have the time to implement them. Please tell
  us, if you can't get along without them. Here is a listing of these
  currently dereleased features:
    ODBC support

  The following procedures received new names in this release:
    sleep (now process-sleep)
    sleep-until (now process-sleep-until)

  network-info, service-info and protocol-info now return #f on non-success.

  The default directory for creating temporary files has changed: It's
  now the value of $TMPDIR if set and /var/tmp otherwise.

  The nth procedure is still there but is now officially obsolete.  It
  will go away in a future release.

** HTML version of the manual
  There is now a HTML version of the scsh manual generated by tex2page

* 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.

Brought to you by the Scheme Underground. Go forth and write elegant systems
    -Olin Shivers, Brian Carlstrom, Martin Gasbichler & Mike Sperber