SCM(April 2006)

NAME
scm - a Scheme Language Interpreter

SYNOPSIS
scm [-a kbytes ] [-muvqib] [--version] [--help]
[[-]-no-init-file] [--no-symbol-case-fold]
[-p int ] [-r feature ] [-h feature ]
[-d filename ] [-f filename ] [-l filename ]
[-c expression ] [-e expression ] [-o dumpname ]
[-- | - | -s] [ filename ] [ arguments ... ]

DESCRIPTION
Scm is a Scheme interpreter.

Upon startup scm loads the file specified by by the environment variable SCM_INIT_PATH or by the parameter IMPLINIT in the makefile (or scmfig.h) if SCM_INIT_PATH is not defined. The makefiles attempt to set IMPLINIT to "Init.scm" in the source directory. Unless the option -no-init-file or --no-init-file occurs in the command line or if scm is being invoked as a script, "Init.scm" checks to see if there is file "ScmInit.scm" in the path specified by the environment variable HOME (or in the current directory if HOME is undefined). If it finds such a file, then it is loaded. "Init.scm" then looks for command input from one of three sources: From an option on the command line, from a file named on the command line, or from standard input.

OPTIONS
The options are processed in the order specified on the command line.

-akbytes
    specifies that scm should allocate an initial heapsize of kbytes. This option, if present, must be the first on the command line.

--no-init-file
    Inhibits the loading of "ScmInit.scm" as described above.

--no-symbol-case-fold
    Symbol (and identifier) names are case-sensitive.

-eexpression

-cexpression
    specifies that the scheme expression expression is to be evaluated. These options are inspired by perl and sh respectively. On Amiga systems the entire option and argument need to be enclosed in quotes. For instance "-e(newline)".

-rfeature
    requires feature. This will load a file from SLIB if that feature is not already supported. If feature is 2, 3, 4, or 5 scm will require the features necessary to support R2RS, R3RS, R4RS, or R5RS, respectively.

-hfeature
    provides feature.

-lfilename

-ffilename
    loads filename. Scm will load the first (unoptioned) file named on the command line if no -c, -e, -f, -l, or -s option precedes it.

-dfilename
    opens (read-only) the extended relational database filename. If filename contains initialization code, it will be run when the database is opened.

-odumpname
    saves the current SCM session as the executable program dumpname. This option works only in SCM builds supporting dump. If options appear on the command line after -o dumpname, then the saved session will continue with processing those options when it is invoked. Otherwise the (new) command line is processed as usual when the saved image is invoked.

-plevel
    sets the prolixity (verboseness) to level. This is the same as the scm command (verbose level ).

-v  (verbose mode) specifies that scm will print prompts, evaluation times, notice of loading files, and garbage collection statistics. This is the same as -p3.

-q  (quiet mode) specifies that scm will print no extra information. This is the same as -p0.

-m  specifies that subsequent loads, evaluations, and user interactions will be with R4RS macro capability. To use a specific R4RS macro implementation from SLIB (instead of SLIB's default) put -r macropackage before -m on the command line.

-u  specifies that subsequent loads, evaluations, and user interactions will be without R4RS macro capability. R4RS macro capability can be restored by a subsequent -m on the command line or from Scheme code.

-i  specifies that scm should run interactively. That means that scm will not terminate until the (quit) or (exit) command is given, even if there are errors. It also sets the prolixity level to 2 if it is less than 2. This will print prompts, evaluation times, and notice of loading files. The prolixity level can be set by subsequent options. If scm is started from a tty, it will assume that it should be interactive unless given a subsequent -b option.

-b  specifies that scm should run non-interactively. That means that scm will terminate after processing the command line or if there are errors.

-s  specifies, by analogy with sh, that further options are to be treated as program arguments.

-   -- specifies that there are no more options on the command line.

ENVIRONMENT VARIABLES

SCM_INIT_PATH
    is the pathname where scm will look for its initialization code. The default is the file "Init.scm" in the source directory.

SCHEME_LIBRARY_PATH
    is the SLIB Scheme library directory.

HOME
    is the directory where "Init.scm" will look for the user initialization file "ScmInit.scm".

SCHEME VARIABLES

*argv*
    contains the list of arguments to the program. *argv* can change during argument processing. This list is suitable for use as an argument to SLIB getopt.

*R4RS-macro*
    controls whether loading and interaction support R4RS macros. Define this in "ScmInit.scm" or files specified on the command line. This can be overridden by subsequent -m and -u options.

*interactive*
    controls interactivity as explained for the -i and -b options. Define this in "ScmInit.scm" or files specified on the command line. This can be overridden by subsequent -i and -b options.

EXAMPLES

% scm foo.scm arg1 arg2 arg3
    Load and execute the contents of foo.scm. Parameters arg1 arg2 and arg3 are stored in the global list *argv*.

% scm -f foo.scm arg1 arg2 arg3
    The same.

% scm -s foo.scm arg1 arg2
    Set *argv* to ("foo.scm" "arg1" "arg2") and enter interactive session.

% scm -e '(display (list-ref *argv* *optind*))' bar
    Print ``bar''

% scm -rpretty-print -r format -i
    Load pretty-print and format and enter interactive mode.

% scm -r5
    Load dynamic-wind, values, and R4RS macros and enter interactive (with macros) mode.

% scm -r5 -r4
    Like above but rev4-optional-procedures are also loaded.

FEATURES

Runs under Amiga, Atari-ST, MacOS, MS-DOS, OS/2, NOS/VE, Unicos, VMS, Unix and similar systems. Support for ASCII and EBCDIC character sets.

Conforms to Revised^5 Report on the Algorithmic Language Scheme and the IEEE P1178 specification.

Support for SICP, R2RS, R3RS, and R4RS scheme code.

Many Common Lisp functions: logand, logor, logxor, lognot, ash, logcount, integer-length, bit-extract, defmacro, macroexpand, macroexpand1, gentemp, defvar, force-output, software-type, get-decoded-time, get-internal-run-time, get-internal-real-time, delete-file, rename-file, copy-tree, acons, and eval.

Char-code-limit, most-positive-fixnum, most-negative-fixnum, and internal-time-units-per-second constants. *Features* and *load-pathname* variables.

Arrays and bit-vectors. String ports and software emulation ports. I/O extensions providing most of ANSI C and POSIX.1 facilities.

User definable responses to interrupts and errors, Process-synchronization primitives, String regular expression matching, and the CURSES screen management package.

Available add-on packages including an interactive debugger, database, X-window graphics, BGI graphics, Motif, and Open-Windows packages.

A compiler (HOBBIT, available separately) and dynamic linking of compiled modules.

Setable levels of monitoring and timing information printed interactively (the `verbose' function). Restart, quit, and exec.

FILES

scm.texi
    Texinfo documentation of scm enhancements, internal representations, and how to extend or include scm in other programs.

AUTHORS
Aubrey Jaffer (jaffer @ alum.mit.edu)
Radey Shouman (shouman @ ne.mediaone.net)

BUGS

SEE ALSO
The SCM home-page:
http://swissnet.ai.mit.edu/~jaffer/SCM.html

The Scheme specifications for details on specific procedures (http://swissnet.ai.mit.edu/ftpdir/scheme-reports/) or

IEEE Std 1178-1990,
IEEE Standard for the Scheme Programming Language,
Institute of Electrical and Electronic Engineers, Inc.,
New York, NY, 1991

Brian Harvey and Matthew Wright
Simply Scheme: Introducing Computer Science_
MIT Press, 1994 ISBN 0-262-08226-8

R. Kent Dybvig, The Scheme Programming Language,
Prentice-Hall Inc, Englewood Cliffs, New Jersey 07632, USA

H. Abelson, G. J. Sussman, and J. Sussman,
Structure and Interpretation of Computer Programs,
The MIT Press, Cambridge, Massachusetts, USA