Replacement wait-online script

wait-online.py

#!/usr/bin/python

from subprocess import check_output
from time import sleep
import click, sys

def is_interface_up(iface):
    try:
        return b'state DOWN' not in check_output(["/usr/bin/ip", "link", "show", "dev", iface]) and \         
            b'inet' in check_output(["/usr/bin/ip", "addr", "show", "dev", iface])                            
    except Exception as ex:
        return False

def wait_online(ifaces, waitsec, maxwait):
    elapsed = 0
    for iface in ifaces:
        while not is_interface_up(iface):
            print('[%] Interface {} is down, sleeping.'.format(iface))
            sleep(waitsec)
            elapsed += waitsec
            
            if elapsed > maxwait:
                print('[!] Unable to bring interfaces up'.format(iface))                                      
                sys.exit(0)
                
        print('[+] Interface {} is online!'.format(iface))                                                    

    sys.exit(0)

@click.command()
@click.option("--waitsec", default=5)
@click.option("--maxwait", default=60)
@click.argument("interfaces", nargs=-1)
def cli(interfaces, waitsec, maxwait):
    if interfaces:
        print('[+] Waiting for interfaces {} to come up'.format(interfaces))                                  
        wait_online(interfaces, waitsec, maxwait)
    else:
        print('[+] No interfaces are specified, exiting'.format(interfaces))                                  
        sys.exit(0)

if __name__ == "__main__":
    cli()