Search a particular config in many files

Shell Programming and Scripting
1

Hi,
Having trouble in our network we would like to implement a second "ip-helper" (to have DHCP redondancy) to do so we have to take all the network elements config (switches and routers) , finds where the particular config is and add a second line. To do so we need to have a list where this ip-helper line is. but we need also to keep the line where "interface ..." is

basically I need to make a script uising awk or other to do the following :

  1. open the files one by one and find the "ip-helper ..."

file1

  ... 
  interface xxxxxx
  ip-helper 10.10.10.1
  ip address 192.168.4.4 255.255.255.0
  ...

or 

interface xxxxxx
  ip address 192.168.4.4 255.255.255.0
  ip-helper 10.10.10.1

file2

 ...
  interface vlan3
  ip address 192.168.4.4 255.255.255.0
  ip-helper 10.10.10.1
...

then I want to have as a result only one file with

result.txt :

filename1(where the text was found)
interface xxxxxx
  ip-helper 10.10.10.1
filename2(where the text was found)
interface xxxxxx
  ip-helper 10.10.10.1
...

complex no ? :eek:
Any help would be appreciate. I didn't do Scripting since years now and I have just got new job that I would like to keep.
Thanks to every contributors.

2

No. Try

awk '/interface/ {IF = $0} /ip-helper/ {print FILENAME; print IF; print}' file1 file2
file1
  interface xxxxxx
  ip-helper 10.10.10.1
file2
  interface vlan3
  ip-helper 10.10.10.1