is_in_specified_subnet.sh

is_in_specified_subnet.sh

#!/bin/bash

###
#
#            Name:  is_in_specified_subnet.sh
#     Description:  A script that detects whether this Mac is on a particular
#                   subnet, as determined by whether the IP starts with a
#                   specific string.
#          Author:  Elliot Jordan <elliot@elliotjordan.com>
#         Created:  2015-09-21
#   Last Modified:  2015-09-21
#         Version:  1.0
#
###

# The beginning segment of a matching IP address (e.g. "10.1.12.")
MATCH="10.1.12."

# Generate list of all active network device ports (e.g. en0, en1).
DEVICE_PORTS="$(ifconfig | awk -F: '/<UP,BROADCAST,SMART,RUNNING,/{print $1}' | sort 2> /dev/null)
$(ifconfig | awk -F: '/<UP,POINTOPOINT,RUNNING,/{print $1}' | sort 2> /dev/null)"

# Flag that switches to "true" if a match is found.
DOES_MATCH="false"

# Iterate through active ports.
for PORT in $DEVICE_PORTS; do

    # Get IP address of this port.
    THIS_IP=$(ifconfig "$PORT" | awk '/inet /{print $2}' 2> /dev/null)
    if [[ "$THIS_IP" != "" ]]; then
        if [[ "$THIS_IP" =~ ^$MATCH ]]; then
            DOES_MATCH="true"
        fi
    fi

done

echo "$DOES_MATCH"

exit 0