Multiple sendevent calls in one command

Tested against BlueStacks 5, should work on any rooted Android system, and Linux systems in general

To write "hello" using 19 commands

If you want to write 'hello' using Android's sendevent, you usually need something like this:

sendevent /dev/input/event3 1 35 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 35 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 18 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 18 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 24 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 24 0
sendevent /dev/input/event3 0 0 0

This is slow, because you have to execute 19 times the sendevent command.

To write "hello" in one single command

Compile the code

g++ -std=c++2a -O3 -g0 sendeventall.cpp

Use

./a.out /dev/input/event3 KEY_H:ud:1#KEY_E:ud:0#KEY_L:ud:0#KEY_L:ud:0#KEY_O:ud:0

or 

./a.out /dev/input/event3 35:ud:1#18:ud:0#38:ud:0#38:ud:0#24:ud:0

or the Python wrapper

sendkeycmd = create_sendkey_command(
    exefile="/data/data/com.termux/files/home/sendevent_multicommands_type_text/a.out",
    device_path="/dev/input/event1",
    text="This is a Test!!! REALLY!!!",
    min_time_key_press=1,
    max_time_key_press=3,
)
print(sendkeycmd)

# output command, can be used with subprocess or directly in the adb/termux shell:
/data/data/com.termux/files/home/sendevent_multicommands_type_text/a.out /dev/input/event1 KEY_LEFTSHIFT:d:0#KEY_T:ud:1#KEY_LEFTSHIFT:u:0#KEY_H:ud:1#KEY_I:ud:1#KEY_S:ud:3#KEY_SPACE:ud:2#KEY_I:ud:1#KEY_S:ud:3#KEY_SPACE:ud:1#KEY_A:ud:1#KEY_SPACE:ud:1#KEY_LEFTSHIFT:d:0#KEY_T:ud:3#KEY_LEFTSHIFT:u:0#KEY_E:ud:2#KEY_S:ud:1#KEY_T:ud:2#KEY_LEFTSHIFT:d:0#KEY_1:ud:3#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_1:ud:1#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_1:ud:3#KEY_LEFTSHIFT:u:0#KEY_SPACE:ud:2#KEY_LEFTSHIFT:d:0#KEY_R:ud:1#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_E:ud:3#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_A:ud:1#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_L:ud:2#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_L:ud:1#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_Y:ud:3#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_1:ud:3#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_1:ud:1#KEY_LEFTSHIFT:u:0#KEY_LEFTSHIFT:d:0#KEY_1:ud:3#KEY_LEFTSHIFT:u:0

Explanation - Token: KEY_H:ud:1 / 35:ud:1

# Tokens are split by "#"

KEY_H or 35 -> keycode "h" (all key codes are available in the source code [linux standard] )
ud -> up and down events - press and release
1 -> sleep 1 ms 

Explanation - Token: KEY_E:ud:0 / 18:ud:0

KEY_E or 18 -> keycode "e" 
ud -> up and down events  - press and release
0 -> sleep 0 ms 

Console (stderr) output:

sendevent /dev/input/event3 1 35 1
sendevent /dev/input/event3 0 0 0
sleeping 1 ms
sendevent /dev/input/event3 1 35 0
sendevent /dev/input/event3 0 0 0
sleeping 1 ms
sendevent /dev/input/event3 1 18 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 18 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 24 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 24 0
sendevent /dev/input/event3 0 0 0

To write "Hello" (first letter upper case) in one command

./a.out /dev/input/event3 KEY_LEFTSHIFT:d:1#KEY_H:ud:1#KEY_LEFTSHIFT:u:1#KEY_E:ud:0#KEY_L:ud:0#KEY_L:ud:0#KEY_O:ud:0

Explanation - Tokens

KEY_LEFTSHIFT:d:1

KEY_LEFTSHIFT -> press "KEY_LEFTSHIFT" 
d -> down event 
1 -> sleep 1 ms 

KEY_H:ud:1

KEY_H -> press and release "h"
ud -> up and down events 
1 -> sleep 1 ms 

KEY_LEFTSHIFT:u:1

KEY_LEFTSHIFT -> release "KEY_LEFTSHIFT" 
u -> up event 
1 -> sleep 1 ms 

sendevent /dev/input/event3 1 42 1
sendevent /dev/input/event3 0 0 0
sleeping 1 ms
sendevent /dev/input/event3 1 35 1
sendevent /dev/input/event3 0 0 0
sleeping 1 ms
sendevent /dev/input/event3 1 35 0
sendevent /dev/input/event3 0 0 0
sleeping 1 ms
sendevent /dev/input/event3 1 42 0
sendevent /dev/input/event3 0 0 0
sleeping 1 ms
sendevent /dev/input/event3 1 18 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 18 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 38 0
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 24 1
sendevent /dev/input/event3 0 0 0
sendevent /dev/input/event3 1 24 0
sendevent /dev/input/event3 0 0 0