[Lazarus] Startup environment: to Gui, or not to GUI?

[Mark Morgan Lloyd]

On 11/04/17 10:30, Mark Morgan Lloyd via Lazarus wrote:
> On 11/04/17 10:00, Henry Vermaak via Lazarus wrote:> On Tue, Apr 11,
> 2017 at 09:15:16AM +0000, Mark Morgan Lloyd via Lazarus wrote:>
> Apologies if this is an FAQ.> > Is there an orthodox way that a Lazarus
> program can very early on look at> how it's been started and decide
> whether it can usefully fall back to a text> mode, e.g. to display help
> info on stdout rather than a messagebox?> isatty() is traditionally used
> for this on POSIX operating systems.It's in unit termio.
> Thanks Henry, I'll check. I know I've used it in the past when deciding
> whether a program was actually being fed piped input etc.

Something like this does appear to work, tested on Linux only.

function notGui(): boolean;

var     i: integer;

begin
   i := IsaTty(Input);
{$ifdef ISGUI }
   exit false;
{$endif ISGUI }
{$ifdef NOGUI }
   exit true;
{$endif NOGUI }
   result := i <> 0
end { notGui } ;

The explicit overrides might be needed during debugging, since the 
involvement of gdb forces the program to think it's being run from a 
shell session.

Looking back through older sources, I've had to jump through hoops- 
reopening the input and using GetFileType() under Windows- to find out 
whether stdin was piped. Fortunately I don't need that here.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]