My super simple ip checking script

Question

i have a small home network with a PC running arch that acts as a NAT router; in the near future i am planning on setting up VPN access on this arch box. i would assume that it is imperative to know the external IP address of the router in order to connect. my ISP is comcast (cable) and they seem to be rather active in changing my DHCP'd address i get from them (in the past 6 months i have had 3 different ones). so i wrote this bash script that runs in the background and monitors the IP of the external interface. its pretty self explanatory; the mails to "vtext.com" are so i can have it texted to me. pointers would be welcome. i am not particularly a programmer, much more just an admin. the awk stuff seems messy, like there should be an easier way to isolate strings than that.... but idk. i run it
#!/bin/bash
# IP CHECK 2.0 (file name/path: /etc/scripts/ipcheck)
# runs in the background and
# requires sleep, mailx & ifconfig
# assumes external interface named "eth0"
# current ip output file path - single-line file containing current address (needs to be writable)
OPATH="/var/ipcheck/currentip"
# Amount of seconds to wait between checks
WAITSECS=300 # 5 mins
# Read previous IP from specified $OPATH file, if it's there
if [ -f "$OPATH" ]; then
OLDIP=`cat $OPATH`;
fi
# Begin main program loop
while :
do
# retrieve new ip using ifconfig
NEWIP=`/sbin/ifconfig eth0 | awk 'BEGIN{FS="inet ";RS=" netmask"}/</{print $2}' | tr -d '\\n' | tr -d ' '`
# print whatever was awk'd and the current date/time to tty11
echo "========= $NEWIP -- `date`" >> /dev/tty11
# if a different NEW IP is detected AND it isn't a null value, then do the following:
# * write the new address out to the OPATH file, replacing the previous value
# * e-mail the new address to my phone via vtext.com
# * e-mail both the old and new addresses to my main e-mail account
# * reset the $OLDIP value as the new one
if [[ "$OLDIP" != "$NEWIP" && "$NEWIP" != "" ]]; then
echo $NEWIP > $OPATH
echo "======= New Address - Old IP: $OLDIP ---- New IP: $NEWIP" >> /dev/tty12
echo "New IP: $NEWIP" | /usr/bin/mailx [email protected]
echo "Old IP: $OLDIP" | /usr/bin/mailx -s "New IP: $NEWIP" [email protected]
OLDIP=$NEWIP
fi
# pause in between checks, then start again
sleep $WAITSECS
done

Answer 1

falconindy wrote:
Isola wrote:
Here's my IP checking script, modified for mailx
#!/bin/bash
curl ifconfig.me | read IP
[ "x$IP" == "x`tail -n1 /tmp/wanip`" ] && exit 0
echo New IP: $IP
echo -n Old IP:
cat /tmp/wanip
echo -n Number of times you had this IP before:
grep $IP /tmp/wanip | wc -l
} | mailx -s "New IP: $IP" [email protected] [email protected]
echo $IP >> /tmp/wanip
This can't possibly work as is... The assignment in the first line happens in a subshell. It's going to be blank in the rest of the script.
Okay I admit, I just wrote that without testing it
edit:
The 2nd line can be changed for this:
read IP < <(curl ifconfig.me) || exit $?
Or
IP=$(curl ifconfig.me) || exit $?
Last edited by Isola (2012-07-01 00:59:39)