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Re: portable terminal

From: John W. Eaton
Subject: Re: portable terminal
Date: Wed, 29 Jul 2020 15:41:46 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0

On 7/29/20 1:54 PM, Rik wrote:
On 07/29/2020 09:40 AM, John W. Eaton wrote:
On 7/29/20 12:31 PM, Rik wrote:

I saw this bit of code in your latest check-in for __debug_octave__.m:

+    if (isunix ())
+      ## FIXME: is there a portable way to run a command in a new window?
+      ## Obviously, gnome-terminal is not always available.
+      command_string = "gnome-terminal -- gdb -p %d";

As far as I'm aware there isn't a 100% working solution.  On the other hand, it probably is possible to do a bit better than one hardcoded terminal.  I happen to use KDE for the desktop and don't have said terminal installed.

I tried xdg-open, but it treats the command as a URL.

I think for a fair number of systems have the alternatives system inherited from Debian (Ubuntu, Mint, etc.) or an implementation copied from Debian (RHEL, Fedora) in which case there is a link at /usr/bin/x-terminal-emulator which will work.

Also, can the default be made to use '-e gdb -p %d'?  That syntax will work with either gnome-terminal or konsole, but the existing one does not.

Sure, please make whatever changes are helpful.  I have no objection to improvements.

I checked in this change

diff -r dce34ad6a6ea -r 7bc89d11ec13 scripts/testfun/__debug_octave__.m
--- a/scripts/testfun/__debug_octave__.m        Wed Jul 29 11:39:52 2020 -0400 +++ b/scripts/testfun/__debug_octave__.m        Wed Jul 29 10:50:07 2020 -0700
@@ -48,14 +48,12 @@ function __debug_octave__ (command_strin

    if (nargin == 0)
-    [status, ~] = system ("gdb --version");
+    status = system ("gdb --version");

The reason for calling system with two outputs here was to capture and ignore the output from gdb so that detecting it would be silent. Do we really want this check to display the version info to the terminal?

-      ## FIXME: is there a portable way to run a command in a new window?
-      ## Obviously, gnome-terminal is not always available.
-      command_string = "gnome-terminal -- gdb -p %d";
+      command_string = "x-terminal-emulator -e gdb -p %d";
      elseif (ispc ())
        command_string = "start gdb -p %d";
      elseif (ismac ())
@@ -65,7 +63,7 @@ function __debug_octave__ (command_strin

-  system (sprintf (command_string, getpid ()));
+  system (sprintf (command_string, getpid ()), "async");


It's a bit more generic, but now I've come across a different issue.  I thought passing the "async" option to system() would allow the spawned process to run separately from Octave.  But, at least for me, this stalls Octave

system ("x-terminal-emulator", "async")

Is this a new bug, or do I not understand system() correctly?

I think that to use "async", it must be the third argument. Probably we don't need the output from the terminal command, so it would be

  system (sprintf (...), false, "async")

but it seems like the terminal emulator exits after executing the program that displays the window anyway, so maybe "async" is not needed, at least on Linux systems? I'm not sure about the others. Originally, I had a separate system command in each branch of the IF command. I don't suppose it hurts to have it.

A separate problem that I see is that when I'm starting Octave from a remote system it doesn't open the terminal window. I'm not sure what's happening there. I have a terminal window open on my desktop system running ssh to connect to another system with X forwarding through the ssh connection. My DISPLAY is set properly. The Octave GUI and Plot windows open correctly. Executing

  system ("emacs", false, "async")

opens a new Emacs window.  But

  system ("x-terminal-emulator", false, "async")

does not.  Weird.


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