jq: Accessing fields with - character in shell script

Question

I am trying to access the field "my-tag" from the following json using jq from a shell script:

json file:

{
    "tag": {
        "value": "hello"
    },
    "my-tag": {
        "value": "hello-my-tag"
    }
}

Shell script:

#!/bin/bash
main()
{
    search="my-tag"
    file="myjson.json"
    value=($(jq ".$search.value" "$file"))
    echo $value
}

main "$@"

On executing this script, I get the following error:

error: tag is not defined
.-tag.value
^^^
1 compile error

How can I extract the field correctly in the shell script?

Answer 1

As a general rule of thumb, I would strongly suggest not placing shell variables within your filters, and use arguments to pass them in.

jq --arg search "$search" '.[$search].value' "$file"

Your filter string is an equivalent to a script. You wouldn't want to modify your script every time you wanted to change a value, you would parameterize it.