How to process in the background without output to the screen

[serkan_tr]

I want to write a program. The purpose of the program is to open cmd and run ROS, enter the command "c:\opt\ros\foxy\x64\setup.bat" in cmd and run the Qt project I wrote in another file. I do not want these processes to appear on the screen.
Necessary information: ROS is a framework that provides an operating system for robot software developers. For ROS to work , c:\opt\ros\foxy\x64\setup.bat must be run in a cmd and processes must be resumed in that cmd.
I also made a Qt project, but my project doesn't work when I tap .exe directly. It works when I first run ROS via cmd and then run .exe via the same cmd.
It's kind of annoying to do this all the time, so I want to write a Qt project that does these steps for me. and I don't want these settings to appear on the screen in the background
Can something like this be done or is there an easier way?

[SGaist]

Hi,

Sounds like you would need some kind of launcher using QProcess to start your ros environment and then your application.

Can you do the launch from a script ?

[Kent-Dorfman]

@serkan_tr said in How to process in the background without output to the screen:

Can something like this be done or is there an easier way?

Well, if you were in a non-windoze environment you would execute a script containing

#! /bin/bash
(
. $PATH_TO_SETUP/setup.sh
$PATH_TO_EXE/qtprogram  2>&1 > /dev/null
)

[serkan_tr]

@Kent-Dorfman
Thank you

[JonB]

@serkan_tr
From Windows you can do the equivalent of @Kent-Dorfman's Linux shell script in a .bat file which you run from QProcess.

However there is a "wrinkle". @Kent-Dorfman's code allows for setup.sh setting environment variables for the following qtprogram call because in . $PATH_TO_SETUP/setup.sh that . at the start causes the setup.sh to be run in the same shell instance as the qtprogram which follows it.

If you Windows .bat file just goes:

c:\opt\ros\foxy\x64\setup.bat
qtprogram

then any environment variables set in setup.bat will not be inherited to qtprogram. And from

For ROS to work , c:\opt\ros\foxy\x64\setup.bat must be run in a cmd and processes must be resumed in that cmd.

I am guessing it may well set such variables.

I believe call is the vital word to achieve what you need from a .bat file. It must be used when that executes any other .bat file which sets environment variables [actually I think this is necessary any time you want to call one .bat file from another and expect it to return into the first .bat file to continue]:

call c:\opt\ros\foxy\x64\setup.bat
qtprogram

If this is put in some setupandrun.bat file you execute that via QProcess::start() (or startDetached()) I am not sure for a .bat file whether you can run it directly via start("/path/to/bat"), you might have to go start("cmd", { "/c", "/path/to/bat" }).

Finally: I just did a test to see if you can avoid the need for the extra setupandrun.bat file you would have to write/distribute. I believe you can do that by:

process->start("cmd", { "/c", R"(c:\opt\ros\foxy\x64\setup.bat & \path\to\qtprogram)" });