JQ：向现有对象添加变量属性

Question

I'm trying to add variable properties to some existing json

{
  "item1": {
    "proerty1": "test"
  },
  "item2": {}
}

So if I do something like this it works

echo $contents | jq --arg ITEM1 $item1 '.[$ITEM1].property2 = "test2"'

But when I try to add more arguments like this it fails:

echo $contents | jq --arg ITEM1 $item1 --arg PROPERTY2 $property2 --arg VALUE $value  '.[$ITEM1].[PROPERTY2] = $VALUE'

The error I get is:

jq: error: syntax error, unexpected '[', expecting FORMAT or QQSTRING_START (Unix shell quoting issues?) at <top-level>, line 1:
.[$ITEM1].[PROPERTY2] = $VALUE
jq: 1 compile error

So I guess += operator wouldn't be the correct way to do this with variables. What would be the correct way to add a propetry where the whole path .item.property and the value itself are variable

Answer 1

The jq filter should be:

.[$ITEM1][$PROPERTY2] = $VALUE

Your query has an extra . .

An alternative:

You could also use setpath/2 , eg

setpath([$ITEM1,$PROPERTY2]; $VALUE)

Aside

It's usually best to quote your shell variables, eg echo "$contents" ...