sed

This week I have to update a couple of yaml files and add a line in too many places. This is the chance to work smarter. So I searched how to add a line after a match and I found this link. So let’s use sed:

$ cat test.yaml 
bgp:
  bgp_as: 65000
  enable: true
  maximum_routes: 12000
  neighbors:
  - description: R1
    route_map_in: RM-IN
  - description: R2
    route_map_in: RM-IN
$ 
$ sed '/route_map_in: RM-IN/a route_map_out: RM-OUT' test.yaml
bgp:
  bgp_as: 65000
  enable: true
  maximum_routes: 12000
  neighbors:
  - description: R1
    route_map_in: RM-IN
route_map_out: RM-OUT
  - description: R2
    route_map_in: RM-IN
route_map_out: RM-OUT

But the I needed to add some spaces to be aligned properly… So I searched again and found this. Now try again adding the spaces we need using “\ ” for each one.

go:1.14.6|py:3.7.3|tomas@athens:~$ sed '/route_map_in: RM-IN/a \ \ \ \ route_map_out: RM-OUT' test.yaml
bgp:
  bgp_as: 65000
  enable: true
  maximum_routes: 12000
  neighbors:
  - description: R1
    route_map_in: RM-IN
    route_map_out: RM-OUT
  - description: R2
    route_map_in: RM-IN
    route_map_out: RM-OUT

So now redirect to a new file to fully check and then you can rename:

$ sed '/route_map_in: RM-IN/a \ \ \ \ route_map_out: RM-OUT' test.yaml > test.yaml.new
$ cat test.yaml.new 
$ mv test.yaml.new test.yaml

Now it is perfect aligned. It is kernel hack, but I am happy enough and saved a lot of time copy/paste and errors for sure.