use subprocess on linux\pi wwith a "grep " command

[korenron]

Hello,
(maybe someone have a simpler solution )
I need to know the status of my modem "UNKNOWN\UP\DOWN"
so I'm running this command:

ip a | grep "wwan"

and this is the response I'm getting:

3: wwan0: <POINTOPOINT,MULTICAST,NOARP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    inet 10.164.47.168/28 scope global wwan0

then I will search for "UNKNOWN\UP\DOWN" in the response and know what to do

I have try to use

result = subprocess.run(['ip', 'a', '| grep wwan' ], stdout=subprocess.PIPE)

but I get this

Command "| grep wwan" is unknown, try "ip address help".

what did I do wrong?
something in the order of the args?

Thanks ,

*** if someone have a better way to check the status - it will also be great

Thanks,

[Gribouillis]

You can try this

import subprocess as sp
p = sp.run('ip a | grep wwan', shell=True, capture_output=True)
print(p.stdout)

Without shell=True, you can also combine processes

ip = sp.Popen(['ip', 'a'], stdout=sp.PIPE)
grep = sp.Popen(['grep', 'wwan'], stdin=ip.stdout, stdout=sp.PIPE)
lines = list(grep.stdout)

[DeaD_EyE]

[andre@andre-Fujitsu-i5 ~]$ ip -j link show wlan0 | python -m json.tool
[
{
"ifindex": 3,
"ifname": "wlan0",
"flags": [
"BROADCAST",
"MULTICAST",
"UP",
"LOWER_UP"
],
"mtu": 1500,
"qdisc": "noqueue",
"operstate": "UP",
"linkmode": "DORMANT",
"group": "default",
"txqlen": 1000,
"link_type": "ether",
"address": "74:e5:f9:4e:73:70",
"broadcast": "ff:ff:ff:ff:ff:ff"
}
]

The tool ip supports json output, which can be processed with Python.
You need the operstate.

import json
from argparse import ArgumentParser
from subprocess import PIPE, run


def get_state(interface):
    cmd = ["ip", "-j", "link", "show", interface]
    proc = run(cmd, encoding="utf8", stdout=PIPE, stderr=PIPE)
    if proc.returncode != 0:
        return proc.stderr

    return json.loads(proc.stdout)[0]["operstate"]


def get_args():
    parser = ArgumentParser()
    parser.add_argument("interface", help="Name of interface to get state from.")
    return parser.parse_args()


def main():
    args = get_args()
    return get_state(args.interface)


if __name__ == "__main__":
    print(main())

Output:
[andre@andre-Fujitsu-i5 ~]$ python get_state.py wlan0
UP
[andre@andre-Fujitsu-i5 ~]$ python get_state.py eno1
Device "eno1" does not exist.

[andre@andre-Fujitsu-i5 ~]$ python get_state.py enp3s0
UP
[andre@andre-Fujitsu-i5 ~]$ python get_state.py lo
UNKNOWN
[andre@andre-Fujitsu-i5 ~]$