nmap-based presence script

presence.sh

#!/bin/bash

SUDO="/usr/bin/sudo"
NMAP="/usr/bin/nmap"
DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )

MACS=$($SUDO $NMAP -sP -n $(ifconfig eth0 | awk '/inet addr:/{print $2;} ' | cut -c6- | awk -F"." '{ print $1"."$2"."$3".0/24" }') | grep "MAC *" | awk -F" " '{ print $3 }')

PRESENCE="$DIR/presence.txt"
UNRECOGNISED="$DIR/unrecognised.txt"
KNOWN="$DIR/known.txt"
ONLINE="$DIR/online.txt"
LOG="$DIR/log.txt"

DATETIME=$(date +%Y%m%d%H%M%S)

if [ ! -f "$PRESENCE" ]; then
  touch "$PRESENCE"
fi

if [ ! -f "$LOG" ]; then
  touch "$LOG"
fi

if [ ! -f "$UNRECOGNISED" ]; then
  touch "$UNRECOGNISED"
fi

if [ ! -f "$ONLINE" ]; then
  touch "$ONLINE"
fi

CURR_PRESENCE="|"

LIST=($MACS)

for MAC in "${LIST[@]}"
do 

  # track macs going online and offline

  found=$(grep "$MAC" "$ONLINE")
  if [ -z "$found" ]; then
    echo "$MAC --> ONLINE"
    echo "$DATETIME MAC ONLINE $MAC" >> "$LOG"
    echo "$MAC" >> "$ONLINE"
  fi

  # track recognised macs

  match=$(grep "$MAC" "$KNOWN")
  if [ -n "$match" ]
    then
      NAME=$(echo $match | cut -c19-)
      CURR_PRESENCE="$CURR_PRESENCE""$NAME""|"

      already=$(grep "$NAME" "$PRESENCE")
      if [ -z "$already" ]; then
        echo "$NAME --> ONLINE"
        echo "$NAME" >> "$PRESENCE"
        echo "$DATETIME PRESENCE ONLINE $NAME" >> "$LOG"
      fi

    else
      recorded=$(grep "$MAC" "$UNRECOGNISED")
      if [ -z "$recorded" ]; then
        echo "$DATETIME $MAC" >> "$UNRECOGNISED"
      fi
  fi

done

# track macs going offline

CHANGED=""
TMP=""
while read PREV_MAC;
do
  if [[ "$MACS" == *"$PREV_MAC"* ]]
    then
      TMP="$TMP""$PREV_MAC"$'\n'
    else
      echo "$PREV_MAC --> OFFLINE"
      echo "$DATETIME MAC OFFLINE $PREV_MAC" >> "$LOG"
      CHANGED=1
    fi
done < "$ONLINE"

if [ -n "$CHANGED" ]; then
  echo -n "$TMP" > "$ONLINE"
fi

# track presences going offline

CHANGED=""
TMP=""
while read PREV_PRESENCE;
do
  _PRESENCE=($PREV_PRESENCE)
  _NAME=${_PRESENCE[0]}
  _IDLE=${_PRESENCE[1]}

  if [[ "$CURR_PRESENCE" == *"|""$_NAME""|"* ]]
    then
      # user is active

      TMP="$TMP""$_NAME"$'\n'

      if [ -n "$_IDLE" ]; then
        # reset previous idle
        CHANGED=1
      fi

    else
      # user is inactive

      if [ -z "$_IDLE" ]
        then
          # just started idling
          TMP="$TMP""$_NAME"" 1"$'\n'
        else
          # already idling, increment the counter
          _IDLE=$((_IDLE + 1))

          if [ "$_IDLE" -gt "10" ]; 
            then
              echo "$_NAME --> OFFLINE"
              echo "$DATETIME PRESENCE OFFLINE $_NAME" >> "$LOG"
            else
              TMP="$TMP""$_NAME"" ""$_IDLE"$'\n'
          fi
      fi

      CHANGED=1
    fi
done < "$PRESENCE"

if [ -n "$CHANGED" ]; then
  echo -n "$TMP" > "$PRESENCE"
fi

Populate a file known.txt with mac addresses and single-world (no spaces!) names, e.g.

00:00:00:00:00:00 PersonA
00:00:00:00:00:01 PersonB
00:00:00:00:00:02 PersonB

Use cron to execute this script every 1 minute, e.g.

* * * * * sudo /path/to/script

Auto-generated files:

• presence.txt - up-to-date list of names detected on the network - any number following the name indicates the number of minutes the presence has idled
• online.txt - up-to-date list of MAC addresses online in last minute
• unrecognised.txt - MAC addresses not in known.txt appended here with date and time (first seen) - the entry won't be removed if the MAC is subsequently added to known.txt, so don't forget to remove the entry manually, or remove the entire unrecognised.txt file to refresh
• log.txt - logs MAC addresses and names going online and offline

An example of this script (running on a raspi) with a web-based front-end (using jQuery.ajax to retrieve the auto-updated presence.txt file containing known "names") can be found at Smartspace Kota Kinabalu.