on-reachable

#!/usr/bin/env python

import argparse
import shlex
import subprocess
import time

argument_parser = argparse.ArgumentParser()
argument_parser.add_argument('ip')
argument_parser.add_argument('--on-reachable', action='append', default=[])
argument_parser.add_argument('--not-reachable', action='append', default=[])
argument_parser.add_argument('--timeout', '-t', type=float)
argument_parser.add_argument('--interval', '-i', type=float, default=1)


def is_reachable(address, timeout=None):
    command = ['ping', '-c', '1', '-q', '-n']
    if timeout is not None:
        command.extend(['-W', str(timeout)])

    command.append(address)
    process = subprocess.run(command, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
    return not process.returncode


def execute(command_string):
    command = shlex.split(command_string)
    return subprocess.run(command)


def main(arguments):
    was_reachable = False
    while True:
        reachable = is_reachable(arguments.ip, arguments.timeout)
        if was_reachable is not reachable:
            was_reachable = reachable
            commands = arguments.on_reachable if reachable else arguments.not_reachable
            for command in commands:
                execute(command)

        time.sleep(arguments.interval)


if __name__ == '__main__':
    arguments = argument_parser.parse_args()
    argument_parser.exit(main(arguments))