Options in linux

[none albert]

It is often times useful to pass options to a turnkey program.
The following may save people to reinvent the wheel.

Note:
$@ is known by @+ analogous to COUNT (C@+).
ARGS is passed to a program, the arguments and the environment.

( ARGC ARGV ARG[] SHIFT-ARGS ENV ) \ AvdH B2sep21
\ For a CSTRING (pointer to zero ended chars) return a STRING.
: Z$@ DUP BEGIN COUNT 0= UNTIL 1- OVER - ;
\ Return the NUMBER of arguments passed by Linux
: ARGC ARGS @ @ ;
\ Return the argument VECTOR passed by Linux
: ARGV ARGS @ CELL+ ;
\ Return the environment POINTER passed by Linux
: ENV ARGS @ $@ 1+ CELLS + ;
\ Find argument INDEX, counting from one. Return as a STRING.
: ARG[] CELLS ARGV + @ Z$@ ;
\ Return POINTER behind the end-0 of the environment.
: ENV0 ENV BEGIN $@ WHILE REPEAT ;
\ Shift the arguments, so as to remove argument 1.
: SHIFT-ARGS ARGV >R
R@ CELL+ CELL+ R@ CELL+ ENV0 R> - MOVE
-1 ARGS @ +! ;
---------------------
: handle-options BEGIN ARGC 1 > DUP IF 1 ARG[] DROP C@ &- = THEN
WHILE 1 ARG[] EVALUATE REPEAT ;

Example of how to use options. Note how we take advantage of
Forth being an interpreter. The first SHIFT-ARGS get rid of the
option. The second SHIFT-ARGS get rid of the parameter.
EVALUATE calculates an address. The minimum search order is most
appropriate to this. In ciforth this is e.g.
ONLY EVALUATE PREVIOUS

\ Execute option -p : set the parallel port address.
: -p SHIFT-ARGS 1 ARG[] HEX EVALUATE ATTACH-PARALLEL-PORT DECIMAL
SHIFT-ARGS ;
\ Execute option -s : set the serial device name.
: -s SHIFT-ARGS 1 ARG[] serial-device$ $! SHIFT-ARGS ;
--
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