Offset IP

offset-ip.sh

###################################################
# Offset an IP address by any number of addresses #
###################################################

offset_ip(){
    IP=$1
    OFFSET=$2

    # Convert IP as hexadecimal number
    IP_HEX=$(printf '%.2X%.2X%.2X%.2X\n' `echo $IP | sed -e 's/\./ /g'`)

    # Add the offset to the IP hexadecimal representation
    NEXT_IP_HEX=$(printf %.8X `echo $(( 0x$IP_HEX + $OFFSET ))`)
    
    # Print the result from hexadecimal representation back to IP string representation
    printf '%d.%d.%d.%d\n' `echo $NEXT_IP_HEX | sed -r 's/(..)/0x\1 /g'`
}

# Examples
# $ offset_ip 192.168.1.2 20
# 192.168.1.22
# $ offset_ip  192.168.1.2 257
# 192.168.2.3