Linux /etc/network/interfaces script for wifi

wlan-scan.sh

#!/bin/sh

if [ $# -ne 1 ]; then
  echo "usage: $0 wlan_interface"
  exit 1
fi
DIRECTORY=`dirname $0`
IFACE=$1

ifconfig $IFACE hw ether `$DIRECTORY/mac_address_reset`

ip link set $IFACE up

sleep 1

SCAN=$( \
iwlist $IFACE scan 2>&1 | grep -v "^$IFACE" | grep -v "^$" | \
    grep 'Address:\|Quality:\|ESSID:\|Mode:\|Encryption key:\|Channel /' | \
    sed -e "s/^\ *//" \
        -e "s/^Cell [0-9]\+ - /|/" \
        -e "s/^|Address: /|AP=/" \
        -e "s/^Quality:\([0-9]\+\)\/.*$/QUALITY=\1/" \
        -e "s/^.*Channel \([0-9]\+\).*$/CHANNEL=\1/" \
        -e "s/^ESSID:/ESSID=/" \
        -e "s/^Mode:/MODE=/" \
        -e "s/^Encryption key:/ENC=/" \
        -e "s/^[^|].*:.*//" \
        -e "s/[ \t#]/~/g" | \
    tr "\n|" "|\n" \
)

ip link set $IFACE down

#echo $SCAN
#exit 0

which=""
while read glob scheme; do
    AP=""; QUALITY=""; CHANNEL=""; ESSID=""; MODE=""; ENC=""
    for i in $SCAN ; do
        for ITEM in $(echo $i | sed -e "s/|/ /g" ) ; do
            # for ESSIDs with spaces
            j=$(echo $ITEM | sed -e "s/~/ /g" )
            case $j in
                AP=*)
                    AP=${j#AP=}
                    ;;
                QUALITY=*)
                    QUALITY=${j#QUALITY=}
                    ;;
                CHANNEL=*)
                    CHANNEL=${j#CHANNEL=}
                    ;;
                ESSID=*)
                    ESSID=$(echo ${j#ESSID=} | sed -e "s/ /_/g" )
                    ;;
                MODE=*)
                    MODE=${j#MODE=}
                    ;;
                ENC=*)
                    ENC=${j#ENC=}
                    ;;
            esac
        done

        case "$AP,$ESSID,$ENC,$MODE,$CHANNEL" in
            $glob)
                echo $scheme
                exit 0
                ;;
        esac
    done
done

exit 1