scripts/wifi.sh

#!/bin/bash
# Finds the strongest unencrypted AP and tries to connect to it via dhcp
# Call this script like "wifi.sh wlan0"
TEMP=/tmp/bestap.tmp
LOCK=/var/lock/bestap.lock
if [ `whoami` != "root" ];then
        echo "Sorry, you need to be root to run this program"
        exit 1
fi

if [[ -z $1 ]];then
        echo "USAGE: $0 device"
        exit 1
else
        interface=$1
fi

# Checking for lock
if [[ -e $LOCK ]];then
        exit 1; # Too simply nothing to do here :)
else
        touch $TEMP $LOCK
fi

# Proggy
iwlist $interface scan > $TEMP
NumAPs=`cat $TEMP | grep ESSID | wc -l`
BestAP=0
BestQuality=-1
for i in `seq 1 $NumAPs`;
do
   # Check if AP is encrypted
   Encryption=`cat $TEMP | grep Encryption | head -n$i | tail -n1 | cut -d":" -f2`
   if [ $Encryption = "off" ]; then
      # Find AP with the highest quality
      QUALITY=`cat $TEMP | grep Quality | head -n$i | tail -n1 | cut -d":" -f2 | cut -d"/" -f1 | sed 's/ //g'`
      QUALITY=`cat $TEMP | grep Quality | head -n$i | tail -n1 | cut -d"=" -f2 | cut -d"/" -f1 | sed 's/ //g'`
      if [ "$QUALITY" -gt "$BestQuality" ]; then
         BestQuality=$QUALITY
         BestAP=$i
      fi
   fi
done
if [ $BestAP -gt 0 ]; then
   # Yay, we found an unencrypted AP:
   echo Connecting to...
   ESSID=`cat $TEMP | grep ESSID | head -n$BestAP | tail -n1 | cut -d'"' -f2`
   echo ESSID=$ESSID
   MODE=`cat $TEMP | grep Mode | head -n$BestAP | tail -n1 | cut -d":" -f2`
   echo Mode=$MODE
   CHANNEL=`cat $TEMP | grep Channel | head -n$BestAP | tail -n1 | cut -d"(" -f2 | sed 's/Channel.//g' | sed 's/)//g' | sed 's/ //g'`
   echo Channel=$CHANNEL
   # Connect
   echo iwconfig $interface essid $ESSID mode $MODE channel $CHANNEL
   if [ -e /etc/dhcpc/dhcpcd-${interface}.pid ]; then
      rm /etc/dhcpc/dhcpcd-${interface}.pid
   fi
   dhcpcd $interface
   # Cleanup
fi
rm -f $TEMP $LOCK