SED delete lines between two pattern matches

Question

I am trying to replace lines between two pattern/string matches using SED see below. I need to delete lines below interface GigabitEthernet0/3 up to inter

Answer 1

Income:

$> cat ./text 
interface GigabitEthernet0/2
 duplex full
 mls qos trust dscp
 spanning-tree portfast
!
interface GigabitEthernet0/3
 mls qos trust dscp
 spanning-tree portfast
!
interface GigabitEthernet0/4
 mls qos trust dscp
!

Outcome:

$> cat ./text | sed '/interface GigabitEthernet0\/3/,/\!/c interface GigabitEthernet0\/3\n!'
interface GigabitEthernet0/2
 duplex full
 mls qos trust dscp
 spanning-tree portfast
!
interface GigabitEthernet0/3
!
interface GigabitEthernet0/4
 mls qos trust dscp
!

Sed can work with multi-line patterns. We just use c command which is changing matched pattern (from interface GigabitEthernet0/3 to !) with interface GigabitEthernet0/3 and !.