pass a argument to spawn

pass a argument to spawn

[comicfanzine]

Hi , i'm trying to do a simple " ls -a " , on Ubuntu .

I tried to associate a string value , because :

   subtype Argument_List is String_List;

But it failed .

Anyway , i'm lost with all the types and subtypes in GNAT.OS_Lib and System.Strings .

So , i don't know how to proceed in the simplier way .

WITH GNAT.OS_Lib ;	USE GNAT.OS_Lib ;
WITH Ada.Text_IO ;	USE Ada.Text_IO ;

procedure console_Ada is

    state_spawn : boolean ;

    arg : Argument_List ( 1..1 ) ;
    -- here the value must be "-a" .

begin

    new_line ;

    put_line ( " Print of your files :") ;

    new_line ;

	Spawn ( "/bin/ls" , arg , state_spawn );
    -- /bin/ls -a

    new_line ;

    put ( " Execution of the program with Spawn ?  : " & Boolean'Image( state_spawn ) ) ;

end console_Ada ;

Re: pass a argument to spawn

[Anh Vo]

On Monday, January 11, 2016 at 5:17:50 PM UTC-8, comicf...@gmail.com wrote:
> Hi , i'm trying to do a simple " ls -a " , on Ubuntu .
> 
> I tried to associate a string value , because :
> 
>    subtype Argument_List is String_List;
> 
> But it failed .
> 
> Anyway , i'm lost with all the types and subtypes in GNAT.OS_Lib and System.Strings .
> 
> So , i don't know how to proceed in the simplier way .
> 
> WITH GNAT.OS_Lib ;	USE GNAT.OS_Lib ;
> WITH Ada.Text_IO ;	USE Ada.Text_IO ;
> 
> procedure console_Ada is
> 
>     state_spawn : boolean ;
> 
>     arg : Argument_List ( 1..1 ) ;
>     -- here the value must be "-a" .
> 
> begin
> 
>     new_line ;
> 
>     put_line ( " Print of your files :") ;
> 
>     new_line ;
> 
> 	Spawn ( "/bin/ls" , arg , state_spawn );
>     -- /bin/ls -a
> 
>     new_line ;
> 
>     put ( " Execution of the program with Spawn ?  : " & Boolean'Image( state_spawn ) ) ;
> 
> end console_Ada ;

Why mess with low level while there is a simpler way. Here is a quick binding to the system call as shown below.

with Interfaces.C;

function Invoke_System (Name :string) return Integer is
	
   C_Name : constant Interfaces.C.Char_Array (1 .. Name'Length + 1) := 
		                                  Interfaces.C.To_C(Name);

   function C_system (Name : System.Address) return Interfaces.C.int;
   pragma Import(C, C_system, "system");

begin
   return integer (C_system(C_Name(1)'address));
end;

procedure Invoke_System (Name : String) is
   Dummy : Integer;
begin
   Dummy := Invoke_System(Name);
end Invoke_System;

--...

declare
   Unix_Command : constant String := "ls -a";
begin
   Invoke_System (Unix_Command);
end;

Anh Vo

Re: pass a argument to spawn

[Per Sandberg]

Well
An argument_list is an array of String_Access and needs to be initialize 
as such.
-------------------------------------------------------------------------
with GNAT.OS_Lib; use GNAT.OS_Lib;
with Ada.Text_IO; use Ada.Text_IO;
procedure Console_Ada is
    State_Spawn : Boolean;
    Arg         : constant Argument_List :=
        (1 => new String'("-a"));
        -- Named association is needed since there is only one argument.
        -- This construct also leaks memory but that does not matter here
        -- since the program terminate immediate.
begin
    Put_Line ("Print of your files :");
    Spawn ("/bin/ls", Arg, State_Spawn);
    Put (" Execution of the program with Spawn ? : " & State_Spawn'Img);
end Console_Ada;
-------------------------------------------------------------------------
/May i also suggest that you look into the GNAT.Expect package.
/Per

Den 2016-01-12 kl. 02:17, skrev comicfanzine@gmail.com:
> Hi , i'm trying to do a simple " ls -a " , on Ubuntu .
>
> I tried to associate a string value , because :
>
>     subtype Argument_List is String_List;
>
> But it failed .
>
> Anyway , i'm lost with all the types and subtypes in GNAT.OS_Lib and System.Strings .
>
> So , i don't know how to proceed in the simplier way .
>
> WITH GNAT.OS_Lib ;	USE GNAT.OS_Lib ;
> WITH Ada.Text_IO ;	USE Ada.Text_IO ;
>
> procedure console_Ada is
>
>      state_spawn : boolean ;
>
>      arg : Argument_List ( 1..1 ) ;
>      -- here the value must be "-a" .
>
> begin
>
>      new_line ;
>
>      put_line ( " Print of your files :") ;
>
>      new_line ;
>
> 	Spawn ( "/bin/ls" , arg , state_spawn );
>      -- /bin/ls -a
>
>      new_line ;
>
>      put ( " Execution of the program with Spawn ?  : " & Boolean'Image( state_spawn ) ) ;
>
> end console_Ada ;
>

Re: pass a argument to spawn

[comicfanzine]

If i understand :

 subtype Argument_List is String_List;

 which is simply :

  type String_List is array (Positive range <>) of String_Access;

 which is a access to the pointer :

  type String_Access is access all String;


Now , in the syntax :

    Arg : constant Argument_List := (1 => new String'("-a"));


If this is a call to the pointer value , why use : "new String'" ?

Normally when i use a String , i never use it like this . 

----------------
Anh Vo = In your exemple you create your own function with Interfaces.C , that can be a better way to use a external program then Spawn , i keep it for later :)
----------------
 Per Sandberg = The GNAT.Expect package is not helping .

It's pretty much , more complicated :/

Re: pass a argument to spawn

[Björn Lundin]

On 2016-01-12 14:48, comicfanzine@gmail.com wrote:
> 
> Now , in the syntax :
>     Arg : constant Argument_List := (1 => new String'("-a"));
> 
> 
> If this is a call to the pointer value , why use : "new String'" ?


new String'("-a");
allocates memory for a string, assigns it the value -a
and returns a pointer/access to it.

It is NOT a string, but access/pointer to it

new Integer'(5)
allocates memory for an integer value, assigns it the value 5
and returns a pointer/access to it.


> Normally when i use a String , i never use it like this .

it is not a String.


-- 
--
Björn

Re: pass a argument to spawn

[comicfanzine]

Björn , i understand much better .
-----------------

I know how to use this procedure :

procedure Spawn
     (Program_Name : String;
      Args         : Argument_List;
      Output_File  : String;
      Success      : out Boolean;
      Return_Code  : out Integer;
      Err_To_Out   : Boolean := True);

His body in the package body is not clear , by the way .

Anyway , i would like to use an array for storage  , instead of : " Output_File  : String; " .

So , maybe it would be simplier to create a spawn procedure with the desired content .

But , i don't know how to do that .
Informations about spawning in Ada are needed .

At this mmoment , that's the problem .

Re: pass a argument to spawn

[Per Sandberg]

Well
 From your questions i expect that you want to achieve something like:
----------------------------------------------------------------
with GNAT.Expect;
with GNAT.String_Split;
with GNAT.OS_Lib;
with Ada.Text_IO; use Ada.Text_IO;
procedure Console_Ada is
    Arg         : constant GNAT.OS_Lib.Argument_List :=
                    (1 => new String'("-a"));
    Status      : aliased Integer := 0;
    S           : GNAT.String_Split.Slice_Set;
begin
    Put_Line ("Print of your files :");
    GNAT.String_Split.Create
      (S => S,
       From => GNAT.Expect.Get_Command_Output
         (Command => "/bin/ls",
          Arguments => Arg,
          Input     => "",
          Status    => Status'Access,
          Err_To_Out => True),
       Separators => ASCII.LF & ASCII.CR);
    for i in 1 .. GNAT.String_Split.Slice_Count (S) loop
       Put_Line (">> " & GNAT.String_Split.Slice (S, i));
    end loop;
    Put (" Execution of the program with Spawn ? : " & Status'Img);
end Console_Ada;

----------------------------------------------------------------

Den 2016-01-12 kl. 20:36, skrev comicfanzine@gmail.com:
> Björn , i understand much better .
> -----------------
>
> I know how to use this procedure :
>
> procedure Spawn
>       (Program_Name : String;
>        Args         : Argument_List;
>        Output_File  : String;
>        Success      : out Boolean;
>        Return_Code  : out Integer;
>        Err_To_Out   : Boolean := True);
>
> His body in the package body is not clear , by the way .
>
> Anyway , i would like to use an array for storage  , instead of : " Output_File  : String; " .
>
> So , maybe it would be simplier to create a spawn procedure with the desired content .
>
> But , i don't know how to do that .
> Informations about spawning in Ada are needed .
>
> At this mmoment , that's the problem .
>
>
>
>
>
>

Re: pass a argument to spawn

[comicfanzine]

 Per Sandberg = Yes that was it .