Question

How do you send keyboard input to a program?

That is, under a Linux GUI, is there a good manual (programmable) way, or tool,
of simulating keyboard input on a running program on Linux, so that I can send
from the command-line, e.g., “Control-T” to a Firefox process and “echo
‘hello’\n” to a Gnome-Terminal process without actually focusing on each of
those processes and typing in directly?

Answer 1

xdotool does have a way of sending keystrokes if limited to a focused window:

WID=`xdotool search "Mozilla Firefox" | head -1`
xdotool windowactivate $WID
xdotool key ctrl+l