Ubuntu – How to close filezilla via terminal

exec false is replacing the current shell by the execution of the command false (here not the shell builtin but /bin/false or whatever false executable that comes first in the PATH) which quickly exits. If the shell was the topmost process running in your terminal emulator, there are no more processes running inside it so the terminal emulator is closed.

This is a an acceptable alternate way to close a terminal, just like would be many similar commands:

exec true
exec sleep 0
exec echo
...

See also: what-does-an-exec-command-do

The typical way to close application gracefully is to use kill -TERM 1234 , where 1234 is the PID of the window. Problem, however, is that graphical applications are designed to listen for a specific signal from X server itself , not listening for the TERM signal.

That means you would need some kind of agent in between you and the X server to communicate that you want to send appropriate signal. You can of course write a C program, however there aready exists wmctrl program ( not-surprisingly written in C ) that does exactly that.

Usage of wmctrl is simple:

wmctrl -c :SELECT: # close window that will be selected with pointer
wmctrl -c :ACTIVE: # close currently active window
wmctrl -ic <numeric id> # close window with specific id in hex

It's not installed by default, so get it with sudo apt-get install wmctrl

There's many uses for wmctrl is far beyond just closing windows, so please see more of my answers and Jacob Vlijm's for examples of scripts where it's been used