2.4 Command-Line Options

Scheme accepts the command-line options detailed in the following sections. The options may appear in any order, with the restriction that the microcode options must appear before the runtime options, and the runtime options must appear before any other arguments on the command line. Any arguments other than these options will generate a warning message when Scheme starts. If you want to define your own command-line options, see Custom Command-line Options.

Note that MIT/GNU Scheme supports only long options, that is, options specified by verbose names, as opposed to short options, which are specified by single characters. As of release 7.7.90, all options start with two hyphens, for compatibility with GNU coding standards (and most modern programs). Prior to this release, options started with a single hyphen. While the single-hyphen style continues to work, it is deprecated and will someday stop working.

These are the microcode options:

--compiler

This option specifies defaults appropriate for loading the compiler. It specifies the use of large sizes, exactly like --large; if the --band option is also specified, that is the only effect of this option. Otherwise, the default band's filename is the value of the environment variable MITSCHEME_COMPILER_BAND, if defined, or compiler.com; the library directories are searched to locate this file.

--edwin

This option specifies defaults appropriate for loading the editor. It specifies the use of large sizes, exactly like --large; if the --band option is also specified, that is the only effect of this option. Otherwise, the default band's filename is the value of the environment variable MITSCHEME_EDWIN_BAND, if defined, or edwin.com; the library directories are searched to locate this file.

--compiler --edwin

If both the --compiler and --edwin options are given, Scheme will load an environment containing both the compiler and the editor. The default band's filename is the value of the environment variable MITSCHEME_ALL_BAND, if defined, or all.com; the library directories are searched to locate this file.

--band filename

Specifies the initial world image file (band) to be loaded. Searches for filename in the working directory and the library directories, using the full pathname of the first readable file of that name. If filename is an absolute pathname (on unix, this means it starts with /), then no search occurs—filename is tested for readability and then used directly. If this option isn't given, the filename is the value of the environment variable MITSCHEME_BAND, or if that isn't defined, runtime.com; in these cases the library directories are searched, but not the working directory.

--large

Specifies that large heap, constant, and stack sizes should be used. These are specified by the environment variables

          MITSCHEME_LARGE_HEAP
          MITSCHEME_LARGE_CONSTANT
          MITSCHEME_LARGE_STACK

If this option isn't given, the small sizes are used, specified by the environment variables

          MITSCHEME_SMALL_HEAP
          MITSCHEME_SMALL_CONSTANT
          MITSCHEME_SMALL_STACK

There are reasonable built-in defaults for all of these environment variables, should any of them be undefined. Note that any or all of the defaults can be individually overridden by the --heap, --constant, and --stack options.

Note: the Scheme expression ‘(print-gc-statistics)’ shows how much heap and constant space is available and in use (see Garbage Collection).

--heap blocks

Specifies the size of the heap in 1024-word blocks. Overrides any default. Normally two such heaps are allocated; bchscheme allocates only one, and uses a disk file for the other.

The size specified by this option is incremented by the amount of heap space needed by the band being loaded. Consequently, --heap specifies how much free space will be available in the heap when Scheme starts, independent of the amount of heap already consumed by the band.

--constant blocks

Specifies the size of constant space in 1024-word blocks. Overrides any default. Constant space holds the compiled code for the runtime system and other subsystems.

--stack blocks

Specifies the size of the stack in 1024-word blocks. Overrides any default. This is Scheme's stack, not the unix stack used by C programs.

--option-summary

Causes Scheme to write an option summary to standard error. This shows the values of all of the settable microcode option variables.

--emacs

Specifies that Scheme is running as a subprocess of GNU Emacs. This option is automatically supplied by GNU Emacs, and should not be given under other circumstances.

--interactive

If this option isn't specified, and Scheme's standard I/O is not a terminal, Scheme will detach itself from its controlling terminal, which prevents it from getting signals sent to the process group of that terminal. If this option is specified, Scheme will not detach itself from the controlling terminal.

This detaching behavior is useful for running Scheme as a background job. For example, using bash, the following will run Scheme as a background job, redirecting its input and output to files, and preventing it from being killed by keyboard interrupts or by logging out:

          scheme < /usr/cph/foo.in > /usr/cph/foo.out 2>&1 &

This option is ignored under non-unix operating systems.

--nocore

Specifies that Scheme should not generate a core dump under any circumstances. If this option is not given, and Scheme terminates abnormally, you will be prompted to decide whether a core dump should be generated.

This option is ignored under non-unix operating systems.

--library path

Sets the library search path to path. This is a list of directories that is searched to find various library files, such as bands. If this option is not given, the value of the environment variable MITSCHEME_LIBRARY_PATH is used; if that isn't defined, the default is used.

On unix, the elements of the list are separated by colons, and the default value is /usr/local/lib/mit-scheme. On PCs, the elements of the list are separated by semicolons, and the default value is c:\scheme\lib.

--utabmd filename

Specifies that filename contains the microcode tables (the microcode tables are information that informs the runtime system about the microcode's structure). Filename is searched for in the working directory and the library directories. If this option isn't given, the filename is the value of the environment variable MITSCHEME_UTABMD_FILE, or if that isn't defined, utabmd.bin; in these cases the library directories are searched, but not the working directory.

--utab is an alternate name for the --utabmd option; at most one of these options may be given.

--fasl filename

Specifies that a cold load should be performed, using filename as the initial file to be loaded. If this option isn't given, a normal load is performed instead. This option may not be used together with the --compiler, --edwin, or --band options. This option is useful only for maintenance and development of the MIT/GNU Scheme runtime system.

In addition to the above, bchscheme recognizes the following command-line options, all of which specify parameters affecting how bchscheme uses disk storage to do garbage collection:

--gc-directory directory

Specifies that directory should be used to create files for garbage collection. If the option is not given, the value of environment variable MITSCHEME_GC_DIRECTORY is used instead, and if that is not defined, a standard temporary directory is used (see TMPDIR in see Runtime Environment Variables).

--gc-file filename

Specifies that filename should be used for garbage collection. If the option is not given, the value of environment variable MITSCHEME_GC_FILE is used, and if this is not defined, a unique filename is generated in the directory specified with --gc-directory.

--gcfile is an alias for --gc-file; at most one of these options should be specified.

--gc-keep

Specifies that the GC file used for garbage collection should not be deleted when Scheme terminates. The GC file is deleted only if the file was created by this invocation of Scheme, and this option is not set.

--gc-start-position number

Specifies the first byte position in the GC file at which the Scheme process can write. If not given, the value of the environment variable MITSCHEME_GC_START_POSITION is used, and if that is not defined, ‘0’ is used, meaning the beginning of the file. The area of the file used (and locked if possible) is the region between --gc-start-position and --gc-end-position.

--gc-end-position number

Specifies the last byte position in the GC file at which the Scheme process can write. If not given, the value of the environment variable MITSCHEME_GC_END_POSITION is used, and if that is not defined, the sum of the start position (as specified by --gc-start-position) and the heap size is used. The area of the file used (and locked if possible) is the region between --gc-start-position and --gc-end-position.

--gc-window-size blocks

Specifies the size of the windows into new space during garbage collection. If this option is not given, the value of environment variable MITSCHEME_GC_WINDOW_SIZE is used instead, and if that is not defined, the value ‘16’ is used.

The following command-line options are only used by an experimental version of bchscheme that uses unix System V-style shared memory, and then only if the gcdrone program is installed in the library directory.

--gc-drone program

Specifies that program should be used as the drone program for overlapped I/O during garbage collection. If the option is not given, the value of environment variable MITSCHEME_GC_DRONE is used instead, and if that is not defined, gcdrone is used.

--gc-read-overlap n

Specifies that Scheme should delegate at most n simultaneous disk read operations during garbage collection. If the option is not given, the value of environment variable MITSCHEME_GC_READ_OVERLAP is used instead, and if that is not defined, ‘0’ is used, disabling overlapped reads.

--gc-write-overlap n

Specifies that Scheme should delegate at most n simultaneous disk write operations during garbage collection. If the option is not given, the value of environment variable MITSCHEME_GC_WRITE_OVERLAP is used instead, and if that is not defined, ‘0’ is used, disabling overlapped writes.

The following options are runtime options. They are processed after the microcode options and after the image file is loaded.

--no-init-file

This option causes Scheme to ignore the ~/.scheme.init or scheme.ini file, normally loaded automatically when Scheme starts (if it exists).

--suspend-file

Under some circumstances Scheme can write out a file called scheme_suspend in the user's home directory.¹ This file is a world image containing the complete state of the Scheme process; restoring this file continues the computation that Scheme was performing at the time the file was written.

Normally this file is never written, but the --suspend-file option enables writing of this file.

--eval expression ...

This option causes Scheme to evaluate the expressions following it on the command line, up to (but not including) the next argument that starts with a hyphen. The expressions are evaluated in the user-initial-environment. Unless explicitly handled, errors during evaluation are silently ignored.

--load file ...

This option causes Scheme to load the files (or lists of files) following it on the command line, up to (but not including) the next argument that starts with a hyphen. The files are loaded in the user-initial-environment. Unless explicitly handled, errors during loading are silently ignored.

The following option is supported only when Edwin is loaded.

--edit

This option causes Edwin to start immediately when Scheme is started.