wifi-autorun-on-connect.installer

#!/usr/bin/env bash
#########################################################################
# WiFi Autorun on Connect Installer                                    #
#                                                                       #
#   Automatically run a script when connected to specific               #
#   WiFi networks.                                                      #
#                                                                       #
# Part of HopeSeekr's BashScripts Collection                            #
# https://github.com/hopeseekr/BashScripts/                             #
#                                                                       #
# Copyright © 2020 Theodore R. Smith <theodore@phpexperts.pro>          #
# GPG Fingerprint: 4BF8 2613 1C34 87AC D28F  2AD8 EB24 A91D D612 5690   #
#                                                                       #
# License: Creative Commons Attribution v4.0 International              #
#########################################################################

# Require this script to be run as the root user.
# @see https://serverfault.com/a/37836/56309
if [[ $(/usr/bin/id -u) -ne 0 ]]; then
    echo "Error: You *MUST* run this as sudo or root!"
    exit 99
fi

if [ "$1" == "--help" ] || [ "$1" == "-h" ]; then
    echo "Usage: wifi-autorun-on-startup.installer [HOTSPOT] [SCRIPT]"
    exit
fi


if [ ! -d "/etc/NetworkManager" ]; then
    echo "Error: This script only works with NetworkManager." >&2
    exit 2
fi

WIFI_HOTSPOT=""
if [ ! -z "$1" ]; then
    if [ ! -f "/etc/NetworkManager/system-connections/${1}.nmconnection" ]; then
        echo "Error: NetworkManager does not know about '${1}'." >&2
        echo "       Please try connecting to it first, retrying this script." >&2
        exit 3
    fi

    WIFI_HOTSPOT="$1"
fi

if [ ! -z "$2" ] &&  [ ! -f "$2" ]; then
    echo "Error: Cannot find a script at '${2}'." >&2
    exit 4
fi

echo "Warning: This script only works with NetworkManager..."
echo ""

function selectHotspot() {
    if [ -z "$WIFI_HOTSPOT" ]; then
        echo "Known Hotspots:" >&2

        HOTSPOTS=()
        local index=0
        local file
        for file in /etc/NetworkManager/system-connections/*.nmconnection; do
            index=$(( $index + 1 ))
            filename=${file##*/system-connections/}
            hotspot=${filename%%.nmconnection}
            HOTSPOTS+=("$hotspot")

            echo "    ${index}) ${hotspot}" >&2
        done

        echo "" >&2
        echo -n "Which hotspot (1-${index})? " >&2
        read hotspot_pick
        hotspot_pick=$(( $hotspot_pick - 1 ))

        echo "${HOTSPOTS[$hotspot_pick]}"
    else
        echo $WIFI_HOTSPOT
    fi
}

WIFI_HOTSPOT=$(selectHotspot)

echo "Chosen wifi network: ${WIFI_HOTSPOT}"

function assertScriptDoesNotExit()
{
    SCRIPT_FILE="/etc/NetworkManager/dispatcher.d/on_connect-${1}.sh"
    if [ -f "$SCRIPT_FILE" ]; then
        echo "WARNING: A startup script for this connection already exists" >&2
        echo "         at '${SCRIPT_FILE}'." >&2
        echo "" >&2
        echo -n "Replace it or quit? [r/Q] " >&2

        local replace_or_quit
        read replace_or_quit
        if [ "$replace_or_quit" != "r" ]; then
            echo "Quitting..." >&2
            exit 5
        fi
    fi
}

assertScriptDoesNotExit "${WIFI_HOTSPOT}"

function grabConnectionUUID()
{
    local nm_conn_file="/etc/NetworkManager/system-connections/${1}.nmconnection"

    if [ ! -f "$nm_conn_file" ]; then
        echo "Error: NetworkManager does not know about '${1}'." >&2
        echo "       Please try connecting to it first, retrying this script." >&2
        exit 3
    fi

    CONNECTION_UUID=$(grep uuid= "$nm_conn_file" | sed 's/^uuid=//')
    echo "Connection UUID: $CONNECTION_UUID"
}

grabConnectionUUID "$WIFI_HOTSPOT"


#############################################################
# Grab the text from an existing file -or- user input...    #
#                                                           #
# Copyright © 2020 Theodore R. Smith                        #
# License: Creative Commons Attribution v4.0 International  #
# From: https://github.com/hopeseekr/BashScripts/           #
# @see https://stackoverflow.com/a/64486155/430062          #
#############################################################
function grabDocument()
{
    if [ ! -z "$1" ] &&  [ -f "$1" ]; then
        echo $(<"$1")
    else
        echo "" >&2
        echo "Please type/paste in bash script you wish to be run when NetworkManager connects to '${WIFI_HOTSPOT}'." >&2
        echo "You should NOT start with '#!/usr/bin/env bash'..." >&2
        echo "Press CTRL+D when finished." >&2
        echo "" >&2

        # Read user input until CTRL+D.
        # @see https://stackoverflow.com/a/38811806/430062
        readarray -t user_input

        # Output as a newline-dilemeted string.
        # @see https://stackoverflow.com/a/15692004/430062
        printf '%s\n' "${user_input[@]}"
    fi
}

N=$'\n'
SCRIPT="#!/usr/bin/env bash${N}"
SCRIPT+="if [[ CONNECTION_UUID=\"${CONNECTION_UUID}\" ]]; then${N}"
SCRIPT+="$(grabDocument "$2")${N}"
SCRIPT+="fi${N}"

# Preserve white spaces and newlines.
# @see https://stackoverflow.com/a/18018422/430062
echo "$SCRIPT" > "$SCRIPT_FILE"

chmod 0755 "$SCRIPT_FILE"

echo ""
echo "Success! An autorun on connect script has been successfully installed for ${WIFI_HOTSPOT}."