Store JSON directly in bash script with variables?

Question

I\'m going to preface by saying that \"no, find a different way to do it\" is an acceptable answer here.

Is there a reliable way to store a short bit of JSON in a b

Answer 1

You could use a here-doc:

foo=$(cat <

By leaving EOF in the first line unquoted, the contents of the here-doc will be subject to parameter expansion, so your $bar expands to whatever you put in there.

If you can have linebreaks in your JSON, you can make it a little more readable:

foo=$(cat <

or even (first indent on each line must be a tab)

foo=$(cat <<-EOF
    {
      "Comment": "Update DNSName.",
      "Changes": [
        {
          "Action": "UPSERT",
          "ResourceRecordSet": {
            "Name": "alex.",
            "Type": "A",
            "AliasTarget": {
              "HostedZoneId": "######",
              "DNSName": "$bar",
              "EvaluateTargetHealth": false
            }
          }
        }
      ]
    }
    EOF
)

and to show how that is stored, including quoting (assuming that bar=baz):

$ declare -p foo
declare -- foo="{
  \"Comment\": \"Update DNSName.\",
  \"Changes\": [
    {
      \"Action\": \"UPSERT\",
      \"ResourceRecordSet\": {
        \"Name\": \"alex.\",
        \"Type\": \"A\",
        \"AliasTarget\": {
          \"HostedZoneId\": \"######\",
          \"DNSName\": \"baz\",
          \"EvaluateTargetHealth\": false
        }
      }
    }
  ]
}"

Because this expands some shell metacharacters, you could run into trouble if your JSON contains something like `, so alternatively, you could assign directly, but be careful about quoting around $bar:

foo='{"Comment":"Update DNSName.","Changes":[{"Action":"UPSERT","ResourceRecordSet":{"Name":"alex.","Type":"A","AliasTarget":{"HostedZoneId":"######","DNSName":"'"$bar"'","EvaluateTargetHealth":false}}}]}'

Notice the quoting for $bar: it's

"'"$bar"'"
│││    │││
│││    ││└ literal double quote
│││    │└ opening syntactical single quote
│││    └ closing syntactical double quote
││└ opening syntactical double quote
│└ closing syntactical single quote
└ literal double quote