Send Text on Public IP Change (part 2)

#!/bin/sh

# Before using, home directory references must be modified to match invoking user.
# Additionally, run touch on ~/.ip-cache prior to first run to avoid issues.

cache='/home/rossiter/.ip-cache'
prev=`/bin/cat $cache`
current=`/usr/bin/wget -qO- http://ipecho.net/plain`

# trap possible wget error
if [ $? != 0 ]; then
   exit 1;
fi

# new IP found
if [ "$current" != "$prev" ]; then
   /home/rossiter/bin/sms 12104584011 "$current"

   # SMS was successfully delivered to Google Voice
   # (impossible to determine whether SMS was delivered to phone)
   if [ $? -eq 0 ]; then
      /bin/echo "$current" > "$cache"
      exit 0

   # SMS send failed
   else
      exit 1;
   fi

# old IP still present
else
   exit 0;
fi