Ada 2012 added a new function in Ada.Environment_Variable:
function Value (Name : in String; Default : in String) return String;
The test is to build this main procedure with the switch -gnat2012:
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Environment_Variables;
use Ada.Environment_Variables;
procedure Main is
EV : constant String := "GNAT_TOTO";
begin
Put_Line (Boolean'Image (Exists (EV)));
Put_Line (Value (EV, "toto"));
Set (EV, "tata");
Put_Line (Boolean'Image (Exists (EV)));
Put_Line (Value (EV, "toto"));
Put_Line (Value (EV));
end Main;
The output of its execution should be:
FALSE
toto
TRUE
tata
tata
Tested on x86_64-pc-linux-gnu, committed on trunk
2013-04-23 Vincent Celier <cel...@adacore.com>
* a-envvar.adb, a-envvar.ads (Value): New.
Index: a-envvar.adb
===================================================================
--- a-envvar.adb (revision 198175)
+++ a-envvar.adb (working copy)
@@ -6,7 +6,7 @@
-- --
-- B o d y --
-- --
--- Copyright (C) 2009-2012, Free Software Foundation, Inc. --
+-- Copyright (C) 2009-2013, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
@@ -223,4 +223,13 @@
end if;
end Value;
+ function Value (Name : String; Default : String) return String is
+ begin
+ if Exists (Name) then
+ return Value (Name);
+
+ else
+ return Default;
+ end if;
+ end Value;
end Ada.Environment_Variables;
Index: a-envvar.ads
===================================================================
--- a-envvar.ads (revision 198175)
+++ a-envvar.ads (working copy)
@@ -23,6 +23,11 @@
-- Constraint_Error is propagated. If the execution environment does not
-- support environment variables, then Program_Error is propagated.
+ function Value (Name : String; Default : String) return String;
+ -- If the external execution environment supports environment variables and
+ -- an environment variable with the given name currently exists, then Value
+ -- returns its value; otherwise, it returns Default.
+
function Exists (Name : String) return Boolean;
-- If the external execution environment supports environment variables and
-- an environment variable with the given name currently exists, then
