Simple script to switch to best WiFi signal if current signal falls below threshold (using nmcli)

switch-wifi

#!/bin/bash -eu

# We don't need to switch if current signal has at least this this strength:
GOOD_ENOUGH=50
# Signal to switch to, must at least have this strength:
BETTER=60

# We use 'autoconnect' here, to later filter SSID's explicitly not
# configured as 'autoconnect'.
KNOWN_SSIDS=$(nmcli -g name,type,autoconnect connection show)
# To speed up, we don't need the most recent data, so don't rescan
WIFI_SIGNALS=$(nmcli -g ssid,signal,in-use dev wifi list --rescan no)
# The in-use field is '*' if it is in use.
CURRENT_SIGNAL=$(awk -F: '{if ($3 == "*") { print $2}}' <<<"${WIFI_SIGNALS}")

echo "Current signal: '${CURRENT_SIGNAL}'"
if [[ "${CURRENT_SIGNAL}" -ge "${GOOD_ENOUGH}" ]]; then
  echo "Current signal is good enough."
  exit
fi

while IFS=':' read -r ssid signal in_use; do
  echo "Signal for '${ssid}': ${signal}"
  if [[ "${signal}" -le "${BETTER}" ]]; then
    echo "No better signal found."
    exit
  fi

  # We check if we know this SSID, and if it is set to autoconnect
  if grep -q "^${ssid}:.*:yes$" <<<"$KNOWN_SSIDS"; then
    echo "Switching to: '${ssid}' (${signal})"
    nmcli connection up "${ssid}"
    exit
  fi
done <<<"$WIFI_SIGNALS"