ifplugd

arch wiki - network configuration/ethernet
not necessary if using dhcpcd, same feature works out of the box
install ifplugd:

pacman -S ifplugd

edit config to change default eth0 device to eno1 at /etc/ifplugd/ifplugd.conf

INTERFACES="eno1"

enable service

systemctl enable ifplugd@eno1.service
systemctl start  ifplugd@eno1.service

can use to disable wifi when ethernet connected and enable wifi when ethernet disconnected
runs /etc/ifplugd/ifplugd.action on up/down with two arguments: name of ethernet interface and whether it went up or down. Shell script inspired by this link:

#!/bin/sh
# disable wifi if ethernet connected and enable wifi if ethernet disconnected

case $2 in
    up)   # ethernet up means wifi down
        iwctl station wlan0 disconnect
        ;;
    down) # ethernet down means wifi up
        # parse `iwctl known-networks list` and connect to most recent network
        iwctl station wlan0 connect "$(/home/stephenhuan/bin/iwd-last-network)"
        ;;
esac

remember to mark as executable!

chmod +x /etc/ifplugd/ifplugd.action

parsing script iwd-last-network simply wraps iwctl known-networks list:

#!/usr/bin/env python3
"""
Script to parse `iwctl known-networks list`
and return the most recently connected network.

iwd version 1.30-1.
"""
import datetime
import subprocess


def __known_networks() -> str:
    """Wraps `iwctl known-networks list`."""
    out = subprocess.run(
        ["iwctl", "known-networks", "list"],
        capture_output=True,
        text=True,
    )
    return out.stdout


def get_date(date: str) -> datetime.datetime:
    """Parse iwctl date format into a datetime object."""
    return datetime.datetime.strptime(date, "%b %d, %H:%M %p")


def get_known_networks() -> list[str]:
    """Parses the output of iwctl."""
    lines = __known_networks().strip().splitlines()
    header = lines[2].lower()
    fields = header.split()[1:]
    start = header.find(" ")
    starts = {field: header.find(field) - start for field in fields}
    offset = {
        field: (starts[field], starts.get(next_field, len(header)))
        for field, next_field in zip(fields, fields[1:] + [None])
    }
    get_field = lambda line, field: line[
        offset[field][0] + line.find(" ") : offset[field][1] + line.find(" ")
    ].strip()
    return [
        (
            get_field(row, "name"),
            get_field(row, "security"),
            get_field(row, "hidden"),
            get_date(" ".join(row.split()[-4:])),
        )
        for row in lines[4:]
    ]


if __name__ == "__main__":
    lines = get_known_networks()
    recent = sorted(lines, key=lambda row: row[-1], reverse=True)
    print(recent[0][0])

hang on shutdown: [ *** ] A stop job is running for ...
forum post
bug tracker
use dhcpcd hook instead?

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ifplugd