creating a nested json file from variables using jq

Question

I have a script where I am storing variables and using that I am trying to create a json output to a file. here is my json build format

#!/bin/bash
JSON_STRING=$(jq -n \
                  --arg configId "$configid" \
                  --arg objectname "tempfile" \
                  --arg artifacts "[{ "name" : "oer", "version" : "$ot" }]" \
                  --arg test "2021" \
                   '$ARGS.named') > output.json

desired json o/p (output.json) -

{ "configId": "c8f", "objectname": "tempfile", "artifacts": [{ "name" : "oer", "version" : "1.01" }], "test" : "2021"}

here I am not getting the desired output. any help would be great

jq in itself has very little to do with Unix/Linux. Not saying it's off-topic here, but that with StackOverflow there might be a larger community with more JSON / jq experts. — Marcus Müller
– Marcus Müller, Commented Nov 8, 2021 at 17:39

glenn jackman · Accepted Answer · 2021-11-09 14:38:47Z

11

I'd do it in 2 steps: (EDIT: artifacts is an array of objects)

inner=$(jq -n --arg name oer \
              --arg version "$ot" \
              '$ARGS.named'
)
final=$(jq -n --arg configId "$configid" \
              --arg objectname "tempfile" \
              --arg test "2021" \
              --argjson artifacts "[$inner]" \
              '$ARGS.named'
)
echo "$final"

{
  "configId": "c8f",
  "objectname": "tempfile",
  "artifacts": [
    {
      "name": "oer",
      "version": "1.01"
    }
  ],  "test": "2021"
}

Add a -c if you want the final output to be one line.

edited Nov 9, 2021 at 14:38

answered Nov 8, 2021 at 22:49

glenn jackman

88.6k16 gold badges124 silver badges179 bronze badges

but my output desired output in the question has array braces after artifacts How do I create that ?

Alex
– Alex

2021-11-09 05:28:56 +00:00
Commented Nov 9, 2021 at 5:28
@Alex in this case, use '[$ARGS.named]' for the first jq.

muru
– muru

2021-11-09 07:53:18 +00:00
Commented Nov 9, 2021 at 7:53
@Alex, missed that, fixed.

glenn jackman
– glenn jackman

2021-11-09 14:38:57 +00:00
Commented Nov 9, 2021 at 14:38

Add a comment |

Kusalananda · Accepted Answer · 2021-11-09 08:36:46Z

The safest way to create JSON on the command line is through using a tool that constructs it for you as jq does. However, since you have a nested structure, you may want to create that sub-structure in a separate call to jq as is shown by glenn jackman.

Another way to do what they show, but in one go:

jq -n \
    --arg configId "$configid" \
    --arg objectname tempfile \
    --argjson artifacts "$( 
        jq -n \
            --arg name oer \
            --arg version "$ot" \
            '$ARGS.named'
    )" \
    --arg test 2021 \
    '$ARGS.named'

We use --argjson rather than --arg to include the JSON document from the inner jq, as it is a JSON document and not a string that needs encoding.

You could also use jo, which may reduce typing a bit,

jo  configId="$configid" \
    objectname=tempfile \
    artifacts="$( jo name=oer version="$ot" )" \
    test=2021

A description of the jo utility is found here: https://jpmens.net/2016/03/05/a-shell-command-to-create-json-jo/

Thanks for the pointer to "jo".

rr0ss0rr
– rr0ss0rr

2022-02-13 17:17:36 +00:00
Commented Feb 13, 2022 at 17:17 — rr0ss0rr
– rr0ss0rr, Commented Feb 13, 2022 at 17:17

terdon · Accepted Answer · 2021-11-08 18:54:25Z

3

You are not getting output because you are saving the output in a variable, so there is nothing to redirect to a file. You can do either this:

variable=$(command)

or this:

command > file

But you cannot do variable=$(command) > file because there is nothing to redirect. So although the above will run and wil create and/or overwrite file, the file will always be empty since you have already saved the command's output in a variable.

So, if you both want to have the output in a variable and save it to a file, you would need something like this:

JSON_STRING=$(jq -n \
                  --arg configId "$configid" \
                  --arg objectname "tempfile" \
                  --arg artifacts "[{ "name" : "oer", "version" : "$ot" }]" \
                  --arg test "2021" \
                   '$ARGS.named')
printf '%s\n' "$JSON_STRING" > output.json

edited Nov 8, 2021 at 18:54

answered Nov 8, 2021 at 17:58

terdon♦

253k69 gold badges481 silver badges719 bronze badges

No but the output comes like this have you noticed "artifacts": "[{ name : oer, version : 1.01 }]" I dont want to have double quotes around the array braces rather I would have them in "name" "oer" "version" "1.01" -------CURRENT O/P--------> "configId": "c8f", "objectname": "tempfile", "artifacts": "[{ name : oer, version : 1.01}]","test": "2021"

Alex
– Alex

2021-11-09 05:25:29 +00:00
Commented Nov 9, 2021 at 5:25

Add a comment |

muru · Accepted Answer · 2021-11-09 07:52:06Z

1

It seems you want artifacts to be treated as a JSON array. If that's the case, use --argjson instead of --arg and fix your quotes:

jq -n \
  --arg configId "$configid" \
  --arg objectname "tempfile" \
  --argjson artifacts "[{ \"name\" : \"oer\", \"version\" : \"$ot\" }]" \
  --arg test "2021" \
   '$ARGS.named'

This should result in:

{
  "configId": "",
  "objectname": "tempfile",
  "artifacts": [
    {
      "name": "oer",
      "version": "1.01"
    }
  ],
  "test": "2021"
}

answered Nov 9, 2021 at 7:52

muru

78.3k16 gold badges214 silver badges320 bronze badges

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