Command line arguments

A few command line arguments are processed by Scheme 48 as it starts up.

scheme48 [-i image] [-h heapsize] [-a argument ...]

-i image

specifies a heap image file to resume. This defaults to a heap image that runs a Scheme command processor. Heap images are created by the ,dump and ,build commands, for which see below.

-h heapsize

specifies how much space should be reserved for allocation. Heapsize is in words (where one word = 4 bytes), and covers both semispaces, only one of which is in use at any given time (except during garbage collection). Cons cells are currently 3 words, so if you want to make sure you can allocate a million cons cells, you should specify -h 6000000 (actually somewhat more than this, to account for the initial heap image and breathing room). The default heap size is 3000000 words. The system will use a larger heap if the specified (or default) size is less than the size of the image being resumed.

-a argument ...

is only useful with images built using ,build. The arguments are passed as a list of strings to the procedure specified in the ,build command as for example:

> (define (f a) (for-each display a) (newline) 0)
> ,build f foo.image
> ,exit
% scheme48vm -i foo.image -a mumble "foo x"
mumblefoo x
%

The usual definition of the s48 or scheme48 command is actually a shell script that starts up the Scheme 48 virtual machine with a -i imagefile specifying the development environment heap image and a -o vm-executable specifying the location of the virtual-machine executable (the executable is needed for loading external code on some versions of Unix; see section * for more information). The file go in the Scheme 48 installation source directory is an example of such a shell script.

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