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

Answer 1

I prefer sed for text manipulation:

# cat test 
1
Exception
2
Exception
3
4
Exception
5
Exception
6
7
8
Exception
9



# sed -i '/Exception/a =========================' test 


# cat test 
1
Exception
=========================
2
Exception
=========================
3
4
Exception
=========================
5
Exception
=========================
6
7
8
Exception
=========================
9