How to enter an idle state in console application?

[Kurt]

I am writing a console application implementing a special web server.  I have outsmarted myself a little, in that it's entirely event driven, based on Indy 10 and TTimer events.  For any GUI application, it will happily sit and wait for events and I don't have to do anything.  I don't know how to do this for a console application.  I need a cross-platform idle do-nothing loop, and don't know the way to do that in FPC/Lazarus.

This thread suggests a loop repeatedly calling Application.ProcessMessages, but that's non-blocking so this will spike the CPU at 100%.  I don't want to Sleep the entire application.  All the threads are behind-the-scenes in Indy10, and I can't see how to sleep the main thread selectively.

What do visual applications do in their idle loop?

[cdbc]

Hi
First off, take a look in TApplication, for the message-loop...
2.nd: what about:

Code: Pascal  [Select][+][-]

1. ...
2. var
3.   Stop: boolean;
4.   S: string;
5. ...
6.   // start your thread shenanigans ;-)
7.   Stop:= false;
8.   repeat
9.     readln(S);
10.     if S = 'q' then Stop:= true;
11.   until Stop;
12. ....
13.  

Just my nickels worth 
Regards Benny

[Kurt]

I was going to open some file and just read it past the end and let that block, and I forgot all about stdin.  I feel dumb now.

And yes, Use the Source.

Thanks for both reminders.

[Kurt]

Now that I've had 30 seconds to think about it, neither seem to work.

TApplication doesn't have it's own message loop.  TApplication.Run passes control to the current widget set's message loop.  Console applications have no widget set, so that does nothing. 

And stdin will get closed when the program runs as a daemon.  I could do as I originally thought, which is open up a random stream and just read it, but it seems inelegant.

EDIT: My thinking is to start a TThread, have that thread do nothing but TThread.Sleep(TM_FORBLOODYEVER), then have the main program Thread.WaitFor() on it. 

[cdbc]

Hi
How about entering a Criticalsection twice?!?
Regards Benny

[rvk]

Can't you not just use the OnCommandGet for Indy?

See https://stackoverflow.com/a/27121006/1037511

[alpine]

Daemons runs usually on Linux, so can't you just:
 

Code: Pascal  [Select][+][-]

1. var
2.   SigIntFlag: Boolean;
3.  
4. procedure DoSigInt(S: cint); cdecl;
5. begin
6.   SigIntFlag := True;
7. end;
8.  
9.   ...
10.   SigIntFlag := False;
11.   FpSignal(SIGINT, @DoSigInt);
12.   while not SigIntFlag do
13.     Sleep(1000);
14.   ...
15.  
16.  

[AlanTheBeast]

I am writing a console application implementing a special web server.  I have outsmarted myself a little, in that it's entirely event driven, based on Indy 10 and TTimer events.  For any GUI application, it will happily sit and wait for events and I don't have to do anything.  I don't know how to do this for a console application.  I need a cross-platform idle do-nothing loop, and don't know the way to do that in FPC/Lazarus.

Code: Pascal  [Select][+][-]

1. Repeat
2.      Sleep(100000);
3. Until false;

F*** elegant.

[jamie]

How about simply using a WaitObject for the INPUT file ?

I believe that works with Winders console!!!!!

[Ten_Mile_Hike]

AHHH.... You are creating a TSR from the ancient days of DOS

[marcov]

I usually use a .waitfor with a tthreadlist.

Put a message to process in the tthreadlist, and signal the condition variable. The thread wakes up, and drains the queue.

The trick would be how to get a shutdown event to signal the list.  On Windows this is easy by using waitmultiple variants.

On *nix that will be harder.