grep command to add end line after every match [duplicate]

Answer 1

You want the following option:

--group-separator=SEP
Use SEP as a group separator. By default SEP is double hyphen (--).

Demo:

$ cat file
before
exception 1
after
foo
bar
before
exception 2
after

$ grep -A 1 -B 1 --group-separator======================== exception file 
before
exception 1
after
=======================
before
exception 2
after