A simple bash tool to manage wifi connections in a single command

wificli.sh

#!/bin/bash

# made by github.com/douxxtech
# Note that this was originally made for a rpi 0 w running rpi os buster lite.

RED='\033[0;31m'
GRN='\033[0;32m'
YEL='\033[1;33m'
NC='\033[0m'

log() {
    local level="$1"
    shift
    local color=""
    case "$level" in
        INFO)  color="$GRN" ;;
        WARN)  color="$YEL" ;;
        ERROR) color="$RED" ;;
        *)     color="$NC" ;;
    esac
    printf "[%s] ${color}%-5s${NC} %s\n" "$(date +%T)" "$level" "$*" >&2
}

WLAN_IF="wlan0"
USB_IF="usb0"
TMP_CONF=""
SSID="$1"
PASS="$2"

usage() {
    echo "Usage:"
    echo "  wificli <SSID> [password]   Connect to Wi-Fi"
    echo "  wificli d                   Disconnect from Wi-Fi and restore USB routing"
    exit 1
}

connect_wifi() {
    if [ -z "$SSID" ]; then
        usage
    fi

    log INFO "Bringing up $WLAN_IF"
    ip link set "$WLAN_IF" up || { log ERROR "Failed to bring up $WLAN_IF"; exit 1; }

    killall -q wpa_supplicant dhclient
    rm -f "/var/run/wpa_supplicant/${WLAN_IF}"

    TMP_CONF=$(mktemp)
    if [ -z "$PASS" ]; then
        log INFO "Generating config for open network"
        cat > "$TMP_CONF" <<EOF
ctrl_interface=/var/run/wpa_supplicant
network={
    ssid="$SSID"
    key_mgmt=NONE
}
EOF
    else
        log INFO "Generating config for secured network"
        wpa_passphrase "$SSID" "$PASS" > "$TMP_CONF"
    fi

    log INFO "Starting wpa_supplicant"
    wpa_supplicant -B -i "$WLAN_IF" -c "$TMP_CONF" || {
        log ERROR "Failed to start wpa_supplicant"
        rm -f "$TMP_CONF"
        exit 1
    }

    sleep 2

    log INFO "Requesting IP via DHCP"
    dhclient -v "$WLAN_IF"
    sleep 5

    IP=$(ip -4 addr show "$WLAN_IF" | grep -oP '(?<=inet\s)\d+(\.\d+){3}')
    if [ -z "$IP" ]; then
        log ERROR "No IP obtained from DHCP"
        disconnect_wifi
        exit 1
    fi

    log INFO "Got IP: $IP"

    GW=$(ip route show default | grep "$WLAN_IF" | awk '{print $3}' | head -n1)

    if [ -n "$GW" ]; then
        log INFO "Setting default route via $GW"
        ip route del default 2>/dev/null
        ip route add default via "$GW" dev "$WLAN_IF"
    else
        log WARN "No default gateway found for $WLAN_IF"
    fi

    rm -f "$TMP_CONF"
    log INFO "Connected to $SSID"
}

disconnect_wifi() {
    log INFO "Disconnecting Wi-Fi"

    killall -q dhclient wpa_supplicant
    rm -f "/var/run/wpa_supplicant/${WLAN_IF}"
    ip addr flush dev "$WLAN_IF"
    ip link set "$WLAN_IF" down

    log INFO "Restoring default route to $USB_IF"
    GW_USB=$(ip route show default | grep "$USB_IF" | awk '{print $3}' | head -n1)
    if [ -n "$GW_USB" ]; then
        ip route del default 2>/dev/null
        ip route add default via "$GW_USB" dev "$USB_IF"
        log INFO "Default route restored to $USB_IF ($GW_USB)"
    else
        log WARN "Could not detect gateway for $USB_IF"
    fi

    log INFO "Wi-Fi disconnected"
}

if [ "$(id -u)" -ne 0 ]; then
    log ERROR "Please run as root or with sudo"
    exit 1
fi

case "$SSID" in
    d)
        disconnect_wifi
        ;;
    "")
        usage
        ;;
    *)
        connect_wifi
        ;;
esac