Aloha fellow slackers -

I'm currently setting up remote access to my email server so that clients can get their email from home/wherever they'd like to be. I've got it working, but I'm on a DSL/DHCP line here and am using DynamicDNS to support it. For the moment, I've simply told postfix to allow relay access from my network name (which is of the format pool-IP-Address-.lsanca.dsl-w.verizon.net) until I can figure out a better way. Since I have dynamic dns already and ddclient running to constantly update my domain name, I'm trying to write a script that takes the output of ddclient -query, which spouts out some data including my current public IP, and route it into the postfix/main.cf file using the combo of sed and postconf commands.

My question is this: I've spent about an hour or two now looking through the sed man page and textinfo documentation and can't figure out how to extract just the IP address from ddclient's output. I envision it something like this in the script:

postconf -e "my_networks=pool-`ddclient -query | sed -[I]some command[I] /regexpForIP/`.lsanca.dsl-w.verizon.net";

I know it's a bit convoluted but to me it seems like the best idea at the moment.

sed s/[^0-9.]//g

So that command would replace every character that's not a number with nothing so that I only end up with numbers? except that it has the . character so I'm not really sure what that intends to accomplish. What would that do?

The logic of this SED command is: "on each line of the file, delete the first instance of any character that is not either a numeral or a period."

I do not understand how that relates to OP's question.....!!!


Here is an incompletely de-bugged IP detector. In this case, it's just deleting all lines that don't contain an IP. It fails--e.g.-- on something like 137.56.23.4567

sed -r '/([0-9][0-9]?{2}\.){3}[0-9][0-9]?{2}/!d'

There are other threads here at LQ with examples of Regexes to find valid IPs.

Thanks pixellany!