How to store values in variables with yq?

Question

I have a yml file, from which I am obtaining a key with yq and I am storing it in a variable in bash, I am trying to do another query with the value of the variable but it does not give the expected result

file.yml

version: '3'
services:
  task_auth:
    environment:
      AWS_API_VERSION: "2016-04-19"
      AWS_CONTAINER_CREDENTIALS_RELATIVE_URI: /creds
      PORT: "8000"
      SES_AWS_ACCESS_KEY: xxxxx
      SES_AWS_SECRET_KEY: xxxxx
    image: xxxxxxx
    ports:
      - "8000:8000"

yq e '(.services | keys)[]'  file.yml

Result:

task_auth

Storing the query in a variable TASK_NAME

TASK_NAME=$(yq e '(.services | keys)[]'  file.yml)

Calling the variable to see the previously stored value

$TASK_NAME

bash: task_auth: command not found

yq eval '.services.$TASK_NAME.environment.PORT' file.yml 

Result

null 

if I execute the command echo $TASK_NAME I get the correct value task_auth but to make queries from yq no

Now when I need this other query I need to use the initial variable, how can I do the query using that value of $TASK_NAME in yq?

Thanks in advance

Answer 1

Provide the Bash variable as environment variable, and inside mikefarah/yq use env to retrieve it:

TASK_NAME="$TASK_NAME" yq e '.services[env(TASK_NAME)].environment.PORT' file.yml

8000

See the manual section Read string environment variable