In general this should be fine to do it this way.
When you click the "X" to close the terminal window, that is sending a "signal" from your desktop (GNOME, KDE, etc.) to the terminal application, telling it to shut itself down. Since you're running MATLAB in this shell it's considered a child process to the terminal application.
So part of the responsibilities of being a parent process, is that you in turn send this same close "signal" to your children.
Now if you understand conceptually what I just explained then let's substitute in a bit more of the real terminology.
First with the "signal", there are actually a whole family of different signals that you can send to Unix processes. To keep it simple there are 4 that you'll often see,
The SIGHUP signal is sent to a process when its controlling terminal
is closed. It was originally designed to notify the process of a
serial line drop. In modern systems, this signal usually means that
controlling pseudo or virtual terminal has been closed.
The SIGTERM signal is a generic signal used to cause program
termination. Unlike SIGKILL, this signal can be blocked, handled, and
ignored. It is the normal way to politely ask a program to terminate.
The SIGINT (“program interrupt”) signal is sent when the user types
the INTR character (normally C-c).
The SIGKILL signal is used to cause immediate program termination. It
cannot be handled or ignored, and is therefore always fatal. It is
also not possible to block this signal.
SIGINT is what gets sent when you use Ctrl+C to "break" a program from the command line while it's in the middle of running.
which one is getting used?
Most likely the
SIGTERM is being called by your windowing environment and being passed down to your terminal. Your terminal is then most likely then sending
SIGHUP down to MATLAB. This signal gives all the processes the opportunity to do any local clean-up (closing files, ending processes, etc.) themselves.
You can send signals yourself using the poorly named command,
kill. So to send the
SIGTERM signal to your terminal or the
SIGHUP to MATLAB, you could determine their PID usingps` and then run this command to send them the signal:
$ kill -SIGTERM <PID>
$ kill -SIGHUP <PID>
You can get a complete list of the signals using this command:
$ kill -l
1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP
6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1
11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM
Notice that the signals have numbers? You'll often times see them used like that instead of by their names:
$ kill -15 <PID>
Or the infamous
-9, which can kill pretty much any process.