Extract values from an array in json in one line in Linux bash with jq

Question

I am extending here my recent question about jq since my requirements changed and I am still confused with map function.

Given such a service-def-test.json (very simplified from my real use case):

{
    "definition": {
        "services": [{
                "image": {
                    "name": "img1",
                    "tag": "2.0.1"
                }
            }, {
                "image": {
                    "name": "img2",
                    "tag": "1.4.0"
                }
            }, {
                "image": {
                    "name": "img3",
                    "tag": "1.2.5"
                }
            }
        ]
    }
}

I now would like to get a one-line list of values:

[img1:2.0.1, img2:1.4.0, img3:1.2.
to store eventually in a COMPONENT_IMAGES variable.

From the previous answer,

jq -r '.definition.services | " "COMPONENT_IMAGES=\"\(map(.image.name, .image.tag) | join(", "))\"" ' service-def-test.json

generates

COMPONENT_IMAGES="img1, 2.0.1, img2, 1.4.0, img3, 1.2.5"

but this I want only 3 items in my output array.

I am looking to get

COMPONENT_IMAGES="img1:2.0.1, img2:1.4.0, img3:1.2.5"

What am I missing here? Thanks!

I don't use jq, but ... would replacing ... map(.image.name, .image.tag) ... with ... map(.image.name:.image.tag) ... be accepted by syntax and give you what you want? — Eric Marceau
– Eric Marceau, Commented Jan 26, 2023 at 20:26

pmf · Accepted Answer · 2023-01-26 20:34:37Z

3

map lets you filter each array item individually. Here, we descend to .image, and concatenate the value of .name, a literal colon ":", and the value of .tag. The mapped array can then be joined with a glue string ", ".

jq -r '
  .definition.services
  | "COMPONENT_IMAGES=\"" + (map(.image | .name + ":" + .tag) | join(", ")) + "\""
'

COMPONENT_IMAGES="img1:2.0.1, img2:1.4.0, img3:1.2.5"

Demo

If you prefer using string interpolation, here's its equivalent:

jq -r '
  .definition.services
  | "COMPONENT_IMAGES=\"\(map(.image | "\(.name):\(.tag)") | join(", "))\""
'

COMPONENT_IMAGES="img1:2.0.1, img2:1.4.0, img3:1.2.5"

Demo

edited Jan 26, 2023 at 20:34

answered Jan 26, 2023 at 20:29

pmf

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4 Comments

Jeff Mercado Over a year ago

Suggestion, you could get rid of adding the literal quotes by just converting the string to json. Functionally the same. "COMPONENT_IMAGES=\(map(...)|...|tojson)"

pmf Over a year ago

@JeffMercado Good idea! @sh would be another option in view of the purpose of the construction ("to store eventually in a COMPONENT_IMAGES variable").

EricBDev Over a year ago

eventually, I need only a space (without ',') as separator, and don't need the "" around so I am using this: "COMPONENTS="+ (map(.image | .name + ":" + .tag) | join(" "))'

EricBDev Over a year ago

fyi, the whole is set in a Gitlab job, and the output from jq is set in a env file ( > extract.env ) and then as artifacts: reports: dotenv: extract.env

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