[USB Foot Pedal] Trigger a terminal command with your foot

README.md

Problem

While working on scripts, I execute it hundreds of times while iterating on it (big fan of baby steps approach).

To run my script, I usually have to switch focus to my terminal & run the last command, which makes me lose a bit of focus after the 10th+ time.

One solution is to use a file monitor that runs a command everytime a file gets modified, but in my experience, for most scripts I want to decide when to rerun the script.

After buying a USB foot pedal, I was wondering how can I use it to automate this small inconvenience.

Solution

Run an arbitrary terminal command everytime we detect a USB device event in Python.

Python Code below

Explanation Video on https://www.youtube.com/watch?v=VaVcv8CMePw

foot_pedal_command_trigger.py

# $ sudo evtest
# No device specified, trying to scan all of /dev/input/event*
# Available devices:
# /dev/input/event24:	PCsensor FootSwitch
# Select the device event number [0-24]: ^C

import os
import argparse
from evdev import InputDevice, ecodes, KeyEvent

RED = '\033[91m'
GREEN='\033[92m'
ENDCOLOR='\033[0m'

parser = argparse.ArgumentParser(description='Process a command on every button press of a foot pedal')
parser.add_argument('--device', required=True,help='Input Device e.g. /dev/input/event22. Find it with $ evtest')
parser.add_argument('cmd',help='Command to be run on every key press')
args = parser.parse_args()

print(args.device)

if os.geteuid() != 0:
    print(f"{RED}USB handling needs root to run{ENDCOLOR}")
    raise Exception('Needs to run as root')

device = InputDevice(args.device)
print(f"{GREEN}{device}{ENDCOLOR}")
print(f"{GREEN}Getting exclusive access to input device{ENDCOLOR}")
print(f"cmd$ {GREEN} {args.cmd}{ENDCOLOR}")
device.grab()
try:
    for event in device.read_loop():
        if event.type == ecodes.EV_KEY and event.value == KeyEvent.key_up:            
            os.system(args.cmd)
finally:
    print(f"{GREEN}Releasing exclusive access to input device{ENDCOLOR}")
    device.ungrab()