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Shell Programming and Scripting
Grabbing variables and comparing
Post 302225810 by kerpm on Sunday 17th of August 2008 04:27:00 AM
08-17-2008
Grabbing variables and comparing
I have two computers with dynamic IP addresses and am using dyndns so that they are identifiable as the same computer even if their IPs change (we'll call them host1.dyndns.com and host2.dyndns.com). I also have a remote server which I would like to store my computers' IP addresses on. There is a file on my remote server which has the IPs that the two hostnames point to. So the file would look like this
111.111.111.111 #host1.dyndns.com
222.222.222.222 #host2.dyndns.com
I need a script that will run this command which gets the IPs of my computers:
/usr/bin/dig +short host1.dyndns.com | /usr/bin/tail -n 1
/usr/bin/dig +short host2.dyndns.com | /usr/bin/tail -n 1
Then compare the result (which is an IP address) to the file that I have described above. If the IP is different from the old one then remove that line and replace it with the new IP. I thought I could do this myself but grabbing the old IP and storing it in a variable and then comparing it to the new IP was beyond me. I don't even know if that is how you should do it. sed/awk is preferable but any language will do
Thanks in advance.
111.111.111.111 #host1.dyndns.com
222.222.222.222 #host2.dyndns.com
I need a script that will run this command which gets the IPs of my computers:
/usr/bin/dig +short host1.dyndns.com | /usr/bin/tail -n 1
/usr/bin/dig +short host2.dyndns.com | /usr/bin/tail -n 1
Then compare the result (which is an IP address) to the file that I have described above. If the IP is different from the old one then remove that line and replace it with the new IP. I thought I could do this myself but grabbing the old IP and storing it in a variable and then comparing it to the new IP was beyond me. I don't even know if that is how you should do it. sed/awk is preferable but any language will do
Thanks in advance.
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LEARN ABOUT REDHAT
ypset
ypset(8) System Manager's Manual ypset(8) NAME
ypset - bind ypbind to a particular NIS server SYNOPSYS
ypset [ -d domain ] [ -h hostname ] server DESCRIPTION
In order to run ypset, ypbind must be initiated with the -ypset or -ypsetme options. See ypbind(8). ypset tells ypbind to get NIS ser- vices for the specified domain from the ypserv(8) process running on server. In cases where several hosts on the local net are supplying NIS services, it is possible for ypbind to rebind to another host even while you attempt to find out if the ypset operation succeeded. For example, you can type: example% ypset host1 example% ypwhich host2 which can be confusing. This is a function of the NIS subsystem's attempt to know always a running NIS server, and occurs when host1 does not respond to ypbind because it is not running ypserv (or is overloaded), and host2, running ypserv, gets the binding. Server indicates the NIS server to bind to, and must be specified as a name or an IP address. This will work only if the node has a cur- rent valid binding for the domain in question, and ypbind has been set to allow use of ypset. In most cases, server should be specified as an IP address. OPTIONS
-d domain Specify a domain other than the default domain as returned by domainname(1). -h hostname Set the NIS binding on host hostname instead of the local machine. SEE ALSO
domainname(8), ypbind(8), ypcat(8), ypmatch(1), ypserv(8), yppoll(8), ypwhich(1) AUTHOR
ypset is part of the yp-tools package, which was written by Thorsten Kukuk <kukuk@suse.de>. YP Tools 2.7 May 1998 ypset(8)