Bash script to switch between wifi networks when they lose connection (works on macOS & Linux)

wifi-switch.sh

#!/bin/bash
# - WiFi switching script -
# Reads from wifis.txt file that has one network per line name=password

echo "Loading known networks list..."

MAX_NETWORKS=0

while IFS='=' read -r var value || [[ -n "$line" ]]; do
    WIFI_NETWORK_NAMES[MAX_NETWORKS]="${var}"
    WIFI_PASSWORDS[MAX_NETWORKS]="${value}"
    ((MAX_NETWORKS++))
done < wifis.txt

printf "Loaded!\n\n"

CURRENT_NETWORK=0

MAX_SECS=5
SECS=$[$MAX_SECS]

CURRENT_OS=3
get_current_os() {
    if (( "${OSTYPE:0:6}" == "darwin" )); then
        CURRENT_OS=0
    elif (( "${OSTYPE:0:5}" == "linux" )); then
        CURRENT_OS=1
    elif (( "${OSTYPE:0:4}" == "msys" )); then
        CURRENT_OS=2
    else
        CURRENT_OS=3
    fi
}
get_current_os

if [ $CURRENT_OS -gt 1 ]; then
    echo "$OSTYPE is not supported, bye!"
    exit 0;
else
    case $CURRENT_OS in
        0)
            echo "Running on MacOS"
            ;;
        1)
            echo "Running on Linux"
            ;;
    esac
fi

AIRPORT="wlan0";
get_current_adapter() {
    case $CURRENT_OS in
        0)
            AIRPORT="$( networksetup -listnetworkserviceorder | grep 'Hardware Port: Wi-Fi' | sed 's/.* //' | sed 's/.$//' )";
            ;;
        1)
            AIRPORT="$( nmcli d | grep -i -a 'wifi' | sed 's/ .*//' )";
            ;;
    esac
}
get_current_adapter

echo "Running on $AIRPORT adapter"

connect_to_current_network() {
    case $CURRENT_OS in
        0)
            networksetup -setairportnetwork $AIRPORT "${WIFI_NETWORK_NAMES[$CURRENT_NETWORK]}" "${WIFI_PASSWORDS[$CURRENT_NETWORK]}" | grep -i -a "Failed"
            ;;
        1)
            iwconfig $AIRPORT essid "${WIFI_NETWORK_NAMES[$CURRENT_NETWORK]}" key s:"${WIFI_PASSWORDS[$CURRENT_NETWORK]}" | grep -i -a "Failed"
            ;;
    esac

    sleep 5
}

get_current_network() {
    case $CURRENT_OS in
        0)
            networksetup -getairportnetwork $AIRPORT
            ;;
        1)
            nmcli d | grep -i -a "wifi"
            ;;
    esac
}

reset_network_adapter() {
    case $CURRENT_OS in
        0)
            networksetup -setairportpower $AIRPORT off
            networksetup -setairportpower $AIRPORT on
            ;;
        1)
            nmcli networking off
            nmcli networking on
            ;;
    esac
}

is_network_alive() {
    ping -q -c 1 -W 1 8.8.8.8 >/dev/null
}

echo "Interval is set to $MAX_SECS"
echo "Total networks is $MAX_NETWORKS"
echo "Connecting to network \"${WIFI_NETWORK_NAMES[$CURRENT_NETWORK]}\""
connect_to_current_network
printf "Connected!\n\n"

while true; do
    if (( $SECS == 0 )); then
        SECS=$[$MAX_SECS]

        if is_network_alive; then
            echo "Connection is still up on \"${WIFI_NETWORK_NAMES[$CURRENT_NETWORK]}\"!"
        else
            echo "Connection on \"${WIFI_NETWORK_NAMES[$CURRENT_NETWORK]}\" is down!"
            echo "Switching networks..."

            CURRENT_NETWORK++
            if (( $CURRENT_NETWORK >= $MAX_NETWORKS )); then
                CURRENT_NETWORK=0;
            fi

            if connect_to_current_network; then
                printf "Failed connecting to \"${WIFI_NETWORK_NAMES[$CURRENT_NETWORK]}\", restarting adapter...\n\n";
                
                reset_network_adapter
                
                sleep 1
            else
                get_current_network
            fi
        fi
    fi

    sleep 1

    SECS=$[$SECS-1]
done

exit 0;