Treating arguments that start with `-' as anonymous arguments

From: T. Kurt Bond (tkb@access.mountain.net)
Date: Wed Jan 14 1998 - 02:55:47 MET

Date: Tue, 13 Jan 1998 20:55:47 -0500 (EST)
Message-Id: <199801140155.UAA12622@bc.mountain.net>
From: "T. Kurt Bond" <tkb@access.mountain.net>
To: caml-list@inria.fr
Subject: Treating arguments that start with `-' as anonymous arguments

[I apologize for the lack of a French version of this message.]

When using the standard module Arg, I would sometimes like to be able
to define an keyword like the POSIX getopt keyword `--', which causes
all the rest of the command line arguments to be treated as anonymous
arguments. The following patch (against 1.07) adds to the Arg.spec
type a constructor, Arg.End, which allows the user to specify this.
For instance, if the following

    let speclist = [
      ("-a", Arg.Unit (fun () -> prerr_endline "this was -a"), "a keyword");
      ("--", Arg.End, "Stop interpreting keywords")
    ] in
    Arg.parse speclist (fun s -> prerr_endline ("anon arg: " ^ s))
      "usage info goes here."

is compiled into a.out and run as follows

    $ ./a.out -a anon -- -a
    this was -a
    anon arg: anon
    anon arg: -a

the second -a gets treated as an anonymous argument.

--- arg.ml.orig Tue Jan 13 20:10:08 1998
+++ arg.ml Tue Jan 13 20:21:11 1998
@@ -18,6 +18,7 @@
   | String of (string -> unit) (* Call the function with a string argument *)
   | Int of (int -> unit) (* Call the function with an int argument *)
   | Float of (float -> unit) (* Call the function with a float argument *)
+ | End (* Treat rest as anonymous arguments *)
 
 exception Bad of string
 
@@ -42,6 +43,9 @@
 ;;
 
 let current = ref 0;;
+(* True if checking options; False if rest of arguments are to be interpeted
+ as anonymous arguments. *)
+let checking_opts = ref true;;
 
 let parse speclist anonfun errmsg =
   let initpos = !current in
@@ -67,7 +71,7 @@
   incr current;
   while !current < l do
     let s = Sys.argv.(!current) in
- if String.length s >= 1 & String.get s 0 = '-' then begin
+ if !checking_opts & String.length s >= 1 & String.get s 0 = '-' then begin
       let action =
         try assoc3 s speclist
         with Not_found -> stop (Unknown s)
@@ -91,6 +95,7 @@
             let arg = Sys.argv.(!current+1) in
             f (float_of_string arg);
             incr current;
+ | End -> checking_opts := false;
         | _ -> stop (Missing s)
       with Bad m -> stop (Message m);
       end;
--- arg.mli.orig Tue Jan 13 20:10:09 1998
+++ arg.mli Tue Jan 13 20:21:34 1998
@@ -42,6 +42,7 @@
   | String of (string -> unit) (* Call the function with a string argument *)
   | Int of (int -> unit) (* Call the function with an int argument *)
   | Float of (float -> unit) (* Call the function with a float argument *)
+ | End (* Treat rest as anonymous arguments *)
         (* The concrete type describing the behavior associated
            with a keyword. *)
  

-- 
T. Kurt Bond, tkb@access.mountain.net

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