jq & bash: make JSON array from variable

Question

I'm using jq to form a JSON in bash from variable values.

Got how to make plain variables

$ VAR="one two three"
$ jq -n "{var:"$VAR"}"
{
  "var": "one two three"
}

But can't make arrays yet. I have

$ echo $ARR
one
two
three

and want to get something like

{
  "arr": ["one", "two", "three"]
}

I only manage to get garbled output like

$ jq -n "{arr: ["$ARR"]}"
{
  "arr": [
    "one
two
three"
  ]
}

How to form JSON array in a correct way? Can jq ever do that?

EDIT: Question was asked when there was only jq 1.3. Now, in jq 1.4, it is possible to do straightly what I asked for, like @JeffMercado and @peak suggested, upvote for them. Won't undo acceptance of @jbr 's answer though.

Answer 1

In jq 1.3 and up you can use the --arg VARIABLE VALUE command-line option:

jq -n --arg v "$VAR" '{"foo": $v}'

I.e., --arg sets a variable to the given value so you can then use $varname in your jq program, and now you don't have to use shell variable interpolation into your jq program.

EDIT: From jq 1.5 and up, you can use --argjson to pass in an array directly, e.g.

jq -n --argjson v '[1,2,3]' '{"foo": $v}'