awk + Print lines before and after match - bash

Question

I know this is a repetitive discussion for most query raised by many person, but I didn't get any apt solution specifically and looking only to awk command utiltiy.
I'm try to filter the MAC and IP address from the ifconfig output.
Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx
inet addr:192.xx.xx.xx Bcast:192.xx.xx.xx Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Currently I'm trying to print by matching HWADDR then checking second line, followed by next line.
awk '/HWaddr/{printf $NF;printf " ";getline;print $2;}' <filename> | cut -c1-18,24-
xx:xx:xx:xx:xx:xx 192.168.xx.xx
my question how to search to previous line. for eg:- If I match IP address for second line , then how to reverse search for the first line , something like
awk '/192/{printf $2;printf " ";<unknown>;}' <filename>
Here I'm matching for IP starts from 192, based on that checking the previous line. May I know what is the reverse search for getline, I meant what's the directive for reverse search
looking only with awk utility

Answer 1

The easiest way to do this is simply to store the previous line in a variable, and then reference that when you need it. For example, with the following awk script:
/192/ {print lastline}
{ lastline=$0 }
If I give it the following put:
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 64:00:6a:7d:06:1a brd ff:ff:ff:ff:ff:ff
inet 192.168.1.24/24 brd 192.168.1.255 scope global dynamic eth0
valid_lft 67513sec preferred_lft 67513sec
inet6 fe80::5da1:2401:a725:d2e0/64 scope link
valid_lft forever preferred_lft forever
I get as output:
link/ether 64:00:6a:7d:06:1a brd ff:ff:ff:ff:ff:ff
Of course, interfaces can have multiple addresses, and this would fail
if your interface look like, for example:
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 64:00:6a:7d:06:1a brd ff:ff:ff:ff:ff:ff
inet 172.16.32.1/24 brd 172.16.32.255 scope global dynamic eth0
valid_lft 67513sec preferred_lft 67513sec
inet 192.168.1.24/24 brd 192.168.1.255 scope global dynamic eth0
valid_lft 67513sec preferred_lft 67513sec
inet6 fe80::5da1:2401:a725:d2e0/64 scope link
valid_lft forever preferred_lft forever
Rather than looking at "the previous line", it's better to explicitly
record the MAC address:
/192/ {print hwaddr}
/link\/ether/ {hwaddr=$0}
This will always print out the value of the previous link/ether line.

Answer 2

Could you please try following and let me know if this helps you.
awk '/[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/{print $2 OFS prev} {prev=$0}' Input_file