Question 136831 in Ubuntu Question posted in
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Ubuntu – How to modify a nested module of yaml file using bash script

I am trying to change one specific word in yaml file using sed command

kind: Pod
metadata:
  name: abc12
spec:
  containers:
  - image: ubuntu:latest
    name: Ubuntu
    imagePullPolicy: IfNotPresent
  - image: ngnix: latest
    name: Nginx
    imagePullPolicy: IfNotPresent
...

Tried using the following command
sed '/^ * image: ngnix:latest/,/^*[^:]*:s/imagePullPolicy: IfNotPresent/imagePullPolicy: {}/' file.yaml

I am required to change the imagePullPolicy content only for ngnix using sed/awk command.

Following is my desired output:

kind: Pod
metadata:
  name: abc12
spec:
  containers:
  - image: ubuntu:latest
    name: Ubuntu
    imagePullPolicy: IfNotPresent
  - image: ngnix: latest
    name: Nginx
    imagePullPolicy: {}
...

Thanks

Tags:

4

Answers


  1. 0

    one case (GNU sed)

    sed -E '
/^s*-s*image:s*ngnix/{
  :top
  N
  /imagePullPolicy/!btop
  s/(imagePullPolicy:).*/1 {}/
}' file.yaml

    However, this may not be generic.

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  2. 0

    Using any POSIX awk:

    $ cat tst.sh
#!/usr/bin/env bash

awk '
    match($0,/^[[:space:]-]*/) {
        if      ( RLENGTH > prevRlength ) { indent++ }
        else if ( RLENGTH < prevRlength ) { indent-- }
        prevRlength = RLENGTH

        key = val = substr($0,RLENGTH+1)
        sub(/[[:space:]]*:.*/,"",key)
        sub(/[^:]*:[[:space:]]*/,"",val)

        indent2key[indent] = key
    }

    (indent == 2) && (indent2key[0] == "spec") && (indent2key[1] == "containers") {
        if ( $1 == "-" ) {
            gotImage = 0
        }

        if ( (key == "image") && (val ~ /^ngnix:/) ) {
            gotImage = 1
        }

        if ( gotImage && (key == "imagePullPolicy") && (val == "IfNotPresent") ) {
            sub(/:.*/,": {}")
        }
    }

    { print }
' "${@:--}"


    $ ./tst.sh file
kind: Pod
metadata:
  name: abc12
spec:
  containers:
  - image: ubuntu:latest
    name: Ubuntu
    imagePullPolicy: IfNotPresent
  - image: ngnix: latest
    name: Nginx
    imagePullPolicy: {}

    The above assumes that image: always comes before imagePullPolicy: as in the example you posted.

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  3. 0

    Using GNU sed

    $ sed -E ':a;/- image: ngnix: latest/,/- image:/{n;s/(imagePullPolicy: ).*/1{}/;ba}' input_file
kind: Pod
metadata:
  name: abc12
spec:
  containers:
  - image: ubuntu:latest
    name: Ubuntu
    imagePullPolicy: IfNotPresent
  - image: ngnix: latest
    name: Nginx
    imagePullPolicy: {}
...
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  4. 0

    Fisrt, fix your YAML line 9: image: ngnix: latest => image: nginx:latest (2 errors).

    Then, use a proper parser, yq:

    yq '(.spec.containers[] | select(.image=="nginx:latest").imagePullPolicy) = {}' file

    Online Demo

    Credits to emanuele6 from [email protected]

    kind: Pod
metadata:
  name: abc12
spec:
  containers:
    - image: ubuntu:latest
      name: Ubuntu
      imagePullPolicy: IfNotPresent
    - image: nginx:latest
      name: Nginx
      imagePullPolicy: {}

    You need a little bit more work to include all needed objects.

    To edit inplace, you can use -yi.

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