The usual way to pass arguments to Gforth programs on the command line is via the -e option, e.g.
gforth -e "123 456" foo.fs -e bye
However, you may want to interpret the command-line arguments directly.
In that case, you can access the (image-specific) command-line arguments
through next-arg:
next-arg ( – addr u ) gforth-0.7 “next-arg”
get the next argument from the OS command line, consuming it; if
there is no argument left, return 0 0.
Here’s an example program echo.fs for next-arg:
: echo ( -- )
begin
next-arg 2dup 0 0 d<> while
type space
repeat
2drop ;
echo cr bye
This can be invoked with
gforth echo.fs hello world
and it will print
hello world
The next lower level of dealing with the OS command line are the following words:
arg ( u – addr count ) gforth-0.2 “arg”
Return the string for the uth command-line argument; returns
0 0 if the access is beyond the last argument. 0 arg
is the program name with which you started Gforth. The next
unprocessed argument is always 1 arg, the one after that is
2 arg etc. All arguments already processed by the system
are deleted. After you have processed an argument, you can delete
it with shift-args.
shift-args ( – ) gforth-0.7 “shift-args”
1 arg is deleted, shifting all following OS command line
parameters to the left by 1, and reducing argc @. This word
can change argv @.
Finally, at the lowest level Gforth provides the following words:
argc ( – addr ) gforth-0.2 “argc”
Variable – the number of command-line arguments (including
the command name). Changed by next-arg and shift-args.
argv ( – addr ) gforth-0.2 “argv”
Variable – a pointer to a vector of pointers to the
command-line arguments (including the command-name). Each argument
is represented as a C-style zero-terminated string. Changed by
next-arg and shift-args.