replace values with variables - jq

Question

I can work out how to use jq to replace a value from a variable,

$ jq -n --arg name bar '{"name":$name}'

{
  "name": "bar"
}

But I am not sure how to replace multiple values.

{
  ...
  "snstopic": {
    "topic-project1": "team-project1-dev",
    "topci-project2": "team-project2-dev",
    ...  (different json files have different number of sns topics)
  },
 ...
}

I set these environment variables:

$ export AWS_DEFAULT_REGION=us-east-2
$ export AWS_ACCOUNT_ID=123456789012
$ export ARN_PREFIX="arn:aws:sns:${AWS_DEFAULT_REGION}:${AWS_ACCOUNT_ID}:"

I want to get output as below

{
  ...
  "snstopic": {
    "topic-project1": "arn:aws:sns:us-east-2:123456789012:team-project1-dev",
    "topci-project2": "arn:aws:sns:us-east-2:123456789012:team-project2-dev",
    ...  (different json files have different number of sns topics
  },
 ...
}

How to add it in all matched keys in .snstopic?

Answer 1

In a nutshell: map_values is your friend.

Let's suppose your template is in the file template.json. Then the following script will perform the specified transformation:

#!/bin/bash
# As far as this example is concerned,
# there is no need to export any variables
AWS_DEFAULT_REGION=us-east-2
AWS_ACCOUNT_ID=123456789012
ARN_PREFIX="arn:aws:sns:${AWS_DEFAULT_REGION}:${AWS_ACCOUNT_ID}:"

jq --arg prefix "$ARN_PREFIX" '
  .snstopic |= map_values($prefix + .)
' template.json

Example

template.json

{
  "snstopic": {
    "topic-project1": "team-project1-dev",
    "topci-project2": "team-project2-dev"
  }
}

Output:

{
  "snstopic": {
    "topic-project1": "arn:aws:sns:us-east-2:123456789012:team-project1-dev",
    "topci-project2": "arn:aws:sns:us-east-2:123456789012:team-project2-dev"
  }
}