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Old 07-10-2007, 03:29 PM   #1
Registered: Dec 2006
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grep/sed/awk - find match, then match on next line

I'm trying to find the right combination of syntax to match first the hme0 and then the 192.168.* from the output of ifconfig -a shown below. It looks like GNU grep has the -A switch but I don't have GNU grep, I have to use the existing tools on a Solaris 10 machine. I've been playing around with sed and awk, but can't get the right combination.

 # ifconfig -a
lo0: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1
        inet netmask ff000000 
lo0:1: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1
        zone zone1
        inet netmask ff000000 
lo0:2: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1
        zone bigzone
        inet netmask ff000000 
hme0: flags=1004843<UP,BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 1500 index 2
        inet netmask ffffff00 broadcast
        ether 8:0:20:ac:46:c9 
hme0:1: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2
        zone zone1
        inet netmask ffffff00 broadcast
hme0:2: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2
        zone bigzone
        inet netmask ffffff00 broadcast
This is what I was using and it worked great until I added zones and the additional IP addresses. If possible I'd like to incorporate a solution into this existing bit below.

if [ "$BASH" ]; then
   if [ "$EUID" -eq 0 ];
         PS1="[\u@\h \W]\n # "
             PROMPT_COMMAND="echo -n [$(/sbin/ifconfig -a |  /usr/bin/awk '{print $2}'| grep 192\.168\.*)]"
             PS1="[\u@\h \W]\n \$ "
             PROMPT_COMMAND="echo -n [$(/sbin/ifconfig -a | /usr/bin/awk '{print $2}'|  
grep  192\.168\.*)]"
   else :
The reason for this is that the machine gets an IP address via DHCP and the IP address changes frequently.

Old 07-10-2007, 04:37 PM   #2
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Do you want just the IP address returned?
$ sed -n '/hme0: /,/inet/{
/inet/s/^ *inet \(192\.168\.[[:digit:]]\{1,3\}\.[[:digit:]]\{1,3\}\) .*/\1/p'} test
I cheated a bit assuming the 192.168. part was fixed.
I used the sed from cygwin to test it.

You might want to check if you need to use "\{1,3\}" or {1,3} for your version of sed. The file "test" I just cut and pasted from your post to test the sed command.

Last edited by jschiwal; 07-10-2007 at 04:40 PM.
Old 07-11-2007, 01:14 AM   #3
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ifconfig -a  | awk '/^hme0: / {nextline=NR+1;next}
     { if ( NR==nextline ) { print "IP is: ",$2 } }
Old 07-11-2007, 08:55 AM   #4
Registered: Dec 2006
Distribution: Red Hat
Posts: 33

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Thanks jschiwal and ghostdog74. I couldn't get the first one to work. In cygwin I get an error sed: -e expression #1, char 85: unterminated `s' command and on Solaris I get a message about the command being garbled. Nonetheless it will be a good educational example to work through what it does and get it working. The second one works and that looks easy enough to put in my command as well as being educational too.

Thanks again for responding.


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