CODEWITHSUNDEEP
bashshelltext-processing
iamr00t
iamr00t

Reputation: 33

Shell Script (Bash) to Find IP Range of a Network

Shell Script (Bash) to Find IP Range of a Network

I am trying to create a shell script to automatically find what the IP Address range is of a network. So far I ran the comamnd:

ifconfig | awk '/broadcast/'

This creates the output:

inet 192.168.1.228  netmask 255.255.255.0  broadcast 192.168.1.255

I'd like for the shell script to take the numbers provided (which I believe is enough to find a range of IP Addresses, but correct me if im wrong) and basically just output a range so for me I think it would be either of these options:

192.168.1.0/24

192.168.1.0-255

192.168.1.*

If this is the way to find an IP Range, then can anyone help me figure out how to display it as a simple output like one of the three options I mentioned before? If this is not the way to find an IP Range, could you please explain how the most accurate way to accomplish this would be. I'm trying to understand networking and shell scripting more so any help would be greatly apprecaiated.

Upvotes: 1

Views: 1543

Answers (1)

Maxim Norin
Maxim Norin

Reputation: 1391

Well, if you are going to use ifconfig, then it should be something like this:

BARRAY=({0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1})

PARAMS=$(ifconfig wlan0 | grep netmask | awk '{print $2" "$4}')

IP_ADDRESS=${PARAMS%% *}
IP_ADDRESS=${IP_ADDRESS//./ }

BINARY_IP_ADDRESS=$(for octet in $IP_ADDRESS; do echo -n ${BARRAY[octet]}" "; done)

BIN_IP_SEP1=${BINARY_IP_ADDRESS//1/1 }
BINARY_IP_ARRAY=( ${BIN_IP_SEP1//0/0 } )

NETMASK=${PARAMS#* }
NETMASK=${NETMASK//./ }

BINARY_NETMASK=$(
for octet in $NETMASK
do
    echo -n ${BARRAY[octet]}" "
done
)

BIN_MASK_SEP1=${BINARY_NETMASK//1/1 }
BINARY_MASK_ARRAY=( ${BIN_MASK_SEP1//0/0 } )

# Count bits in MASK ARRAY
BITS_COUNT=0
for i in ${BINARY_MASK_ARRAY[@]}
do
    [ "$i" == "1" ] && BITS_COUNT=$((BITS_COUNT + 1))
done

# Count address
NEW_ADDRESS=""
for i in {0..31}
do
    [ $(($i % 8)) -ne 0 ] || NEW_ADDRESS+=" "
    if [ "${BINARY_MASK_ARRAY[$i]}" == "1" ]
    then
        NEW_ADDRESS+="${BINARY_IP_ARRAY[$i]}"
    else
        NEW_ADDRESS+="${BINARY_MASK_ARRAY[$i]}"
    fi
done

# Convert binary to decimal
DECIMAL_ADDRESS=`echo $(for octet in $NEW_ADDRESS; do echo $((2#$octet)); done)`
DECIMAL_ADDRESS=${DECIMAL_ADDRESS// /.}

# Final result
echo $DECIMAL_ADDRESS/$BITS_COUNT

If you are going to use "ip addr show" then just correct PARAMS calculations according to received data. Anyway, only this line uses external commands, the rest of the script is in pure bash. I hope it helps.

Upvotes: 1

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