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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Help with constructing an Ada Shell
Date: Fri, 30 Oct 2015 09:10:49 +0000
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Date: 2015-10-30T09:10:49+00:00
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(1) I don't know why you want to use access String at all, at any rate
for the command (I see that Argument_List involves access to strings,
necessary in Ada to support ragged arrays).

(2) Spawn.Program_Name is the program to be spawned, Spawn.Arguments are
the arguments to that program, and shouldn't include the program unless
you want to execute it on itself.

(3) Wasn't there a discussion here recently about needing to supply the
full path to the program? (e.g. "/bin/ls" - I think you may have this
sorted already)

(4) The code you've posted doesn't compile.

The code below "works" provided the command you give it is "/bin/ls" - I
converted it into a procedure, & I haven't bothered with parsing the
command into Program_Name and Arguments, or with cleanup.

with Ada.Text_IO; use Ada.Text_IO;

with GNAT.OS_Lib; use GNAT.OS_Lib;
with GNAT.Strings;

procedure Ada_Shell is
   procedure Execute_System (Command : String);
   procedure Main is
      package IO renames Ada.Text_IO;
   begin
      IO.Put_Line("Welcome to ash! This is an extreme work in progress.");
      Main_Loop:
      loop
	 IO.Put("ash> ");
         declare
            Input : constant String := IO.Get_Line;
         begin
	    if Input = "quit" then
	       exit Main_Loop;
	    else
	       Execute_System (Input);
	    end if;
         end;
      end loop Main_Loop;
   end Main;

   procedure Execute_System (Command : String) is
      Result : Integer;
      Arguments : Argument_List := (1 => new String'("ada_shell.adb"));
   begin
      Spawn (Program_Name => Command,
	     Args => Arguments,
	     Output_File_Descriptor => Standout,
	     Return_Code => Result);
      Put_Line(Integer'Image(Result));
   end Execute_System;
begin
   Main;
end Ada_Shell;