Re: Unix environment variables

[dkusu@atc-1s.hac.com (David Kusuda)]

In article 5qk@huron.eel.ufl.edu, joel.rudy@comm.hq.af.mil (Joel Rudy) writes:
>What is the easiest way to access a Unix environment variable via Ada.  We
>are using SunAda 2.1.1 on a Solaris 2.3 operating system.
>

The following program was compiled under both SunAda 1.1j and VADS 6.2 (HP Self-Hosted)
running under SunOS 4.1.3 and HP-UX9.05, respectively.

with A_Strings;
with C_Strings;
with Text_IO;
with U_Env;

procedure ShowEnv is
--
--  Purpose:
--    This program displays the value associated with an environment
--    variable entered on the command line.
--
--  Notes:
--    This program uses a non-standard Ada package, U_Env, to gain
--    access to the command line parameters and the definition of the
--    environment variable.
--

  --  RENAMING DECLARATIONS

  package ASTR renames A_Strings;
  package CSTR renames C_Strings;
  package TIO  renames Text_IO;
  package UENV renames U_Env;

  function "=" (L, R : CSTR.C_String) return Boolean renames CSTR."=";


  --  LOCAL SUBPROGRAM SPECIFICATIONS

  procedure Lookup (Env_Var : ASTR.A_String);
  --
  --  Purpose:
  --    Performs the actual lookup of the environment variable.
  --
  --  Raises:
  --    None.
  --
  --  Notes:
  --    None.
  --


  --  LOCAL SUBPROGAM BODY

  procedure Lookup (Env_Var : ASTR.A_String) is
  --
  --  Notes:
  --    If UENV.Getenv returns a null value, the environment variable
  --    is undefined.
  --

    Lookup_String : CSTR.C_String := 
        UENV.Getenv (CSTR.Convert_A_to_C (Env_Var));
    
  begin  -- Lookup
    if Lookup_String /= null then
      TIO.Put_Line (Env_Var.S & " = " & CSTR.To_String (Lookup_String));
    else
      TIO.Put_Line (Env_Var.S & " is not defined");
    end if;
  end Lookup;
 

begin  -- ShowEnv

  --
  -- Make sure that at least one environment variable was entered on the
  -- command line.
  --
  if UENV.Argc < 2 then
    TIO.Put_Line ("Usage::" & UENV.Argv (0).S & 
        " [environment variable...]");
    return;
  end if;

  for I in 1 .. UENV.Argc - 1 loop
    Lookup (UENV.Argv (I));
  end loop;

end ShowEnv;