Xdotool is an automation tool in Linux, something like AutoHotKey (AHK) for Windows. Below show some examples of it’s usage in a shell script.

# Type ABC
xdotool key A
xdotool key B
xdotool key C

# Tab 3 times
xdotool key Tab
xdotool key Tab
xdotool key Tab

# Type 20
xdotool key 2
xdotool key 0

xdotool key Down
xdotool key Left
xdotool key Right
xdotool key Return

# Use sleep to wait
sleep 0.5

# Multiple keys
xdotool key ctrl+c
xdotool key Alt+Tab
xdotool key ctrl+f
xdotool key ctrl+v
xdotool key enter
xdotool key super+e

# Loops
for n in {1..1};
do
    xdotool key ctrl+c
    xdotool key Alt+Tab

	# Inner loop
    for n in {1..8};
    do
        xdotool key Shift_L+Right
    done
done