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[SOLVED] Problem running external program under Linux
maurobio:
Dear ALL,
I am struck with a strange problem when attempting to run an external program from a Lazarus GUI application under Linux.
I cannot distribute my real application at this time, but it is a relatively straightforward program which executes a C program, passing the name of text file as its only argument and counts the lines in the file; the program then enters a command loop where the user must type 'quit' in order to exit the program. Under Windows, the application works fine, but it fails under Linux. without issuing any error messages.
I am running Lazarus 1.8.2 under Lubuntu 18.04.5 LTS. I have installed Lazarus from the Ubuntu repositories, and therefore that is not the most recent version.
The only reasonable explanation I can find for this problem is that it may be related to that old version of Lazarus. However, before updating, I would like to be sure that it is really the problem. Could someone give it a try under a more recent version of Lazarus for Linux?
My sample code is attached. I hope that perusal of the code will make the problem easier to understand.
Thanks in advance!
With best wishes,
rsz:
Hi,
I don't have a windows machine to compare to right now but I believe the issue you are experiencing is due to how Linux handles console applications differently than Windows. I assume you expect a command prompt to be opened on Linux when the counter program is run?
On Linux you must execute a terminal emulator explicitly (such as xterm) and then pass it arguments to execute your counter program rather than launching the counter program directly.
Jurassic Pork:
hello,
have you tried to launch your compiled program in a xterm ? if you launch your program in the IDE , display the console In/out window -> View/Debug Windows/Console In/Output may be View/Debug Windows/Console Terminal in your Lazarus version.
Friendly, J.P
lucamar:
The C program seems to always return exit code 0; in *nix you should instead (or also) check ExitStatus, which will tell you if there was some problem running the program irrespective of what the program itself returns as ExitCode.
maurobio:
Dear ALL,
Thank you very much indeed for your replies. However, I am still at a loss. I could not fully understand the issue with 'xterm'. But as far as I can see, a console program cannot be executed from a GUI application under Linux in the same way it can be under Windows.
How do I 'execute a terminal emulator explicitly', as suggested by @rsz? Could an example be provided? Also, I would appreciate a tip on how to check ExitStatus as suggested by @lucamar. Unfortunately, none of the explanations provided in the links below mention GUI applications:
https://wiki.freepascal.org/Executing_External_Programs#Using_fdisk_with_sudo_on_Linux
https://forum.lazarus.freepascal.org/index.php?topic=10462.0
I attach a slightly updated version of my sample code, now including a 'runcounter.pas' program as a console-mode application, which works fine under both Linux and Windows.
Thanks again for your time and patience!
With best wishes,
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