Exiting the terminal vs Closing the terminal

Context:-

I am running a process in bash with & appended i.e in background mode. The process has a while(1) i.e it will run forever. My bash is parent and my process becomes the child. I want to learn how Kernel handles the child when parent is terminated.

Observations:-

1. If I exit the terminal (using exit command from the terminal), /lib/systemd/systemd --user becomes the parent process of the child
2. If I kill the terminal process (using kill) from another terminal, same result as above
3. If I close the terminal using cross icon, child process gets terminated too

Question:-

How is closing different from killing/exiting?

There are different kind of signals in linux. When you exit terminal, the signal sent is different from the signal which is sent when you close terminal by clicking on x. Try going through termination signals to find how closing and exiting terminal is different from each other.

I used ping in a gnome-terminal window and I can confirm your observations. I think it is problematic, that a process can be left running without anywhere to communicate. I will try to interpret what I notice (but I do not claim that I understand why, maybe to allow programs with an own GUI to work without nohup after exit from bash, when started in a terminal window).

• When I exit I am exiting from bash running in the terminal window, and ping continues to run, but has nowhere to write.

• When I kill the process, I kill the bash process in the terminal window. I did not find an explicit gnome-terminal process to kill, because the process /usr/lib/gnome-terminal/gnome-terminal-server runs them all. I am not sure that this is what you were doing, but it is what I guess.

• When I close the window (with the x button) I exit from the window process (which in turn forces its child processes to stop including bash and ping). This is an obvious difference from the two previous cases.

When I do the corresponding exercise with xterm, there will be a separate process with the name 'xterm'.

• When I exit I am exiting from bash running in the terminal window, and ping continues to run, but has nowhere to write.

• When I kill the process, I kill the xterm process of the terminal window, (which in turn forces its child processes to stop, including bash and ping).

• When I close the window (with the x button) I exit from the window process (which in turn forces its child processes to stop, including bash and ping).

You know already, that you can use nohup (together with &) if you want the child process to continue after closing the terminal window, where child process was started.

Edit 1: Final comment:

From man bash

If a command is terminated by the control operator &, the shell executes the command in the background in a subshell. The shell does not wait for the command to finish, and the return status is 0.

We have noticed that there is no signal to stop the subshell and the process started in/from that subshell, when bash is exited, at least not when run in a terminal window. But the calling terminal window is closed. I think, that after bash is exited, the terminal window no longer knows of the subshell and the process started in/from that subshell, and therefore it cannot stop them.

Edit 2: I asked for help at Unix & Linux - Please read the answers.

The process launched like this ./myprocess & are child of the parent bash process opened by the terminal program. The sign & wont help you to close the terminal window before the end of a long process.

What you are looking for is the command nohup

user@host:~$ nohup bash -c '/path/to/myprocess'

More info : http://manpages.ubuntu.com/manpages/impish/en/man1/nohup.1.html
Some Examples: https://linuxhint.com/nohup_command_linux/