From owner-freebsd-questions  Sun Dec  9  8:33: 1 2001
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From: "Oliver, Michael W." <oliver.michael@gargantuan.com>
To: "'jacks@sage-american.com'" <jacks@sage-american.com>,
	freebsd-questions@freebsd.org
Cc: "Oliver, Michael W." <oliver.michael@gargantuan.com>
Subject: RE: Scripting help
Date: Sun, 9 Dec 2001 11:32:53 -0500 
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Jack,

Well, this will be my first script written from scratch, so please be kind
if I dork it up!  Try this:






#!/bin/sh

while [ 1 ]
do
    
    LAST_KNOWN_IP=`cat last_known_ip_file`
    CURRENT_IP=`ifconfig tun0 | grep inet | awk ' { print $2; } '`

    if [ -z "$LAST_KNOWN_IP"]
        then
            # run your dns ping program here using $CURRENT_IP
            echo $CURRENT_IP >last_known_ip_file
            continue
    fi

    if [ "$LAST_KNOWN_IP" = "$CURRENT_IP" ]
        then
            sleep 30
            continue
        else
            # run your dns ping program here using $CURRENT_IP
            echo $CURRENT_IP >last_known_ip_file
    fi

done

EOF








Please let me know how it turns out ;-)

===========
Michael Oliver









 

> -----Original Message-----
> From: jacks@sage-american.com [mailto:jacks@sage-american.com] 
> Sent: Sunday, December 09, 2001 11:02 AM
> To: freebsd-questions@freebsd.org
> Subject: Scripting help
> 
> 
> I have just set up an experimental FBSD 4.4-STABLE server 
> using DSL with
> dynamic ip. Using ZoneEdit DNS services, the DNS can be 
> updated with a cron
> script to still point to the proper name. I'm doing that now 
> using cron to
> run the update script every 8 hours (the connection usually 
> runs for weeks
> at a time without disconnect).
> 
> However, I had rather have a script that runs every so often 
> (xminutes) and
> doesn't bother the DNS server unless and ONLY if a changed in 
> the dynamic
> IP has occured as a result of disconnect/reconnect. Here are 
> the functions
> I see needed, but scripting language is not yet a decent 
> skill of mine. I
> suspect others using dynamic IPs have this same need: Any guidence
> appreciated once again. (I've looked at the ipcheck that uses 
> Python, but
> rather not go that route if possible to do the simple 
> approach below). 
> 
> BEGIN (my crude) SCRIPT:
> #!/bin/sh
> PATH=/usr/local/bin:/usr/bin:/bin
> ## This script would be run by cron every x_minutes
> ## (files needed: "last_known_ip" and "my_current_ip")
> ## Contents of last_known_ip (placed there manually at for 
> first output
> ## by running ifconfig tun0 > last_known_ip
> 
> tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1492
>         inet 64.xxx.xx.20 --> 64.xxx.xx.254 netmask 0xffffffff 
>         Opened by PID 149
> 
> ## Run update to my_current_ip file
> # function: ifconfig tun0 > my_current_ip
> 
> ##.... so the "my_current_ip" file would contain output of:
> tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1492
>         inet 64.xxx.xx.20 --> 64.xxx.xx.254 netmask 0xffffffff 
>         Opened by PID 149
> 
> ## Now make comparison to see if dynamic ip has changed and 
> update DNS if
> changed. 
> # function: look in my_current_ip and find the current ip 
> (64.xxx.xx.20)
> # function: look in last_known_ip file and find ip (64.xxx.xx.66)
> # function: if not same, then run DNS_ping_program to update 
> (ping command
> here)
> ## If change detected, update comparison file
> # function: ifconfig tun0 > last_known_ip
> # function: if same ip, then do nothing
> END OF SCRIPT
> 
> The above may be a crude approach, but best way I can define 
> the job for
> now....
> 
> Best regards,
> Jack L. Stone,
> Server Admin
> 
> Sage-American
> http://www.sage-american.com
> jacks@sage-american.com
> 
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