I need to make a console app that can run on Linux. It would be a simple thing I believed, but no...

I cannot get the ClrScr command working, it just puts strange
characters on the screen instead of clearing it.
I started with a Console app in Lazarus and just added this piece of
code:
  { add your program here }
  repeat
    ClrScr;  //Needs Crt in uses
    Write('Enter command: ');
    Readln(FCheck);
  until FCheck = 'q';

But the console debug window just shows a bunch of control characters (square with 001B inside) plus [6n [H [m [H [2JEnter command: And every command I enter results in a new line being displayed rather than staying on the same line and erasing the previous output.

What am I doing wrong?

...

But the console debug window just shows a bunch of control characters (square with 001B inside) plus [6n [H [m [H [2JEnter command: And every command I enter results in a new line being displayed rather than staying on the same line and erasing the previous output.

UPDATE:
It seems to be caused by the Lazarus debug console window! If I go to the dir where the program resides in my terminal (both local and via SSH) and execute ~/tmp/project1 then it looks OK.

So my question now changes to:
Why does the debug window show different output than the actual terminal console?

I am using Lazarus 1.6 release and fpc 3.0.0 both built from svn sources on a Raspberry Pi3 with Raspbian Jessie if that matters.

The console respects the special terminal control characters. The debug window does not respect these characters, and just prints them out to screen. I am not sure this can be properly handled. Maybe there is an option that can be given to xterm to respect the characters.

If you are debugging using SSH, then you probably need to add the -t option.

Michael.

The console window in which the shell and app run might have different commands, depending on what's actually being used (i.e. xterm, an SSH session from a remote system and so on). The console window will have an associated $TERM shell description, and strictly speaking the program that wants to clear the screen should refer to this possibly using curses or libtinto.

I don't know whether the ClrScr procedure refers to libtinfo, or what properties libtinfo thinks the debug window has. It could probably be argued that the debug window should set TERM to indicate that it doesn't obey commands, but I'd suggest that if the program does a ClrScr then the programmer wants notification of this and it should probably /not/ wipe earlier debug output. After all, the debug window is there for debugging, not for normal interaction.

No. It just uses ansi escape characters.

Michael.

I am comparing to how it works in Delphi (7)...
When I program a console program in Delphi and run it from within the IDE it creates the console window and the interactions are shown there.
All Writeln() output shows up as is and the program stops for input on ReadLn() commands etc.

When I started my program in Lazarus nothing showed up at all so I had to google for it and then I was directed towards the menu "View/Debug Windows/Terminal Output" which displays a window titled "Console".
This is the window I refer to and it does not behave like the real terminal...

If OTOH I open a terminal window and navigate to the project dir and start the executable produced by Lazarus, then it behaves as expected.

I am working to transfer my GUI test program into a terminal program with no GUI output so it can be started via the console to map my TCP interactions.
Then I don't have to access any GUI at all to get the port forwarding to work. The target RPi is located in Texas behind a slow Internet connection while I am in Sweden close to Stockholm. A long ways away..

I access the site via VPN but bringing up a TightVNC GUI is no fun due to the latencies caused by the slow Internet speed. SSH via PuTTY works much better and I plan on using screen to run the mapper program while I can continue to work in the terminal base.

No, it does not. Because it is not a real terminal and does not obey the ANSI codes to control the terminal.

Michael.

Indeed it is not a terminal.
AFAIK it's a pseudoterminal based upon a TMemo or TSynEdit (too lazy to look it up).
The code is in $(LazarusDir)/debugger/pseudoterminaldlg.pp

There is a bugreport already about it's behaviour (echoing control characters) in http://bugs.freepascal.org/view.php?id=22349

Feel free to post enhencements.

Bart