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From: Emile8 <pocchiola.yves@gmail.com>
Newsgroups: comp.lang.ada
Subject: ACCESS TO SYSTEM VARIABLES
Date: Mon, 7 Mar 2011 01:34:24 -0800 (PST)
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Date: 2011-03-07T01:34:24-08:00
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On Linux I want to know the number of lines and columns of my working
terminal. When on the command line I call by hand the system variables
$LINES and $COLUMNS, I get the right answers.

When I try to do the same from a program written in Gnat Ada 2005
(Year 2010) using the specialized package Ada.Environment_Variables,
as in the following code called from the same terminal, I get no
answer for COLUMNS and LINES as if the corresponding system variables
do not exist (I get a correct answer for PATH).


with Ada.Environment_Variables; use Ada.Environment_Variables;
with Ada.Text_Io; use Ada.Text_Io;

procedure Print_Env is
begin
Put_Line("Columns : " & Value("COLUMNS"));
Put_Line("Lines : " & Value("LINES"));
Put_Line("Path : " & Value("PATH"));
end Print_Env;


I would like to understand the reasons of this behavior. Are there
different kinds of system variables in Linux ? Those as HOME, PATH
whose values depend only on the user session and those as LINES,
COLUMNS defined for each used terminal. Is there a way in Ada to
overcome this limitation ?