Sorting a JSON file by outer object name

Question

I have a json file input.json thus:

{
   "foo":{
       "prefix":"abc",
       "body":[1,2,3]
   },
   "bar":{
       "prefix":"def",
       "body":[4,5,6]    
   }
}

I would like to sort it by the outer object names, with "bar" coming before "foo" in alphabetical order like so:

{
   "bar":{
       "prefix":"def",
       "body":[4,5,6]    
   },
   "foo":{
       "prefix":"abc",
       "body":[1,2,3]
   }
}

to produce file output.json.

Versions of this question have been asked of Java/Javascript (here and here)

Is there a way to accomplish this using a command line tool like sed/awk or boost.json?

Objects in JS/JSON are unordered bags of key-value pairs, the property order has no inherent meaning. Why is the order important to you? — knittl, Feb 14 '23 at 16:30
@knittl (As always, things are quite complicated.) I have VSCode snippets as json files where the trigger keywords are names of outermost objects in this file. Visual Studio IDE snippets are not json files. They are stored in a different format with the trigger keywords themselves being file names allowing one to sort by their filename in Windows explorer. I am trying to match the two sets of snippets. I am not sure there is any other way to do this but sort the json file. — Tryer, Feb 14 '23 at 16:35

score 2 · Accepted Answer · answered Feb 14 '23 at 16:31

2

Using jq, you could use the keys built-in to get the key names in sorted order and form the corresponding value object

jq 'keys[] as $k | { ($k) : .[$k] }' json

Note that jq does have a field --sort-keys option, which cannot be used here, as it internally sorts the inner level objects as well.

answered Feb 14 '23 at 16:31

Inian

This does work for me. TY! The output prints `4`, `5`, `6`, etc., on separate lines. Is there a way to make the output exactly match the input file (in terms of total number of lines in the files) with only the specific lines of texts interchanged? – Tryer Feb 14 '23 at 16:43
1

@Tryer jq does a default JSON formatting of the input, which unfortunately it doesn't allow to control for specific fields – Inian Feb 14 '23 at 16:48
1

re reformatting: see e.g https://stackoverflow.com/questions/75428312/custom-json-output-formatting-with-jq – peak Feb 14 '23 at 17:17
1

To produce the desired output as given in the Q, you'd have to adapt this approach along the lines of: `[keys[] as $k | {($k): .[$k]} ] | add` – peak Feb 15 '23 at 02:23
@peak yes indeed. I had to modify the suggested answer based on your correction to exactly get the output as I wanted in the OP. Your method also works perfectly. Hope Inian corrects his answer. – Tryer Feb 15 '23 at 04:44

peak · Answer 2 · 2023-02-15T02:25:26.197

1

Here's a variable-free jq solution:

to_entries | sort_by(.key) | from_entries

It is also worth noting that gojq, the Go implementation of jq, currently always sorts the keys within all JSON objects.

edited Feb 15 '23 at 02:25

answered Feb 14 '23 at 19:58

peak

Just to make sure I understand your answer -- should this be `jq to_entries...` instead of just `to_entries...` ? I had to install `jq` on my machine. It is not clear in your answer whether the utility itself is `jq` or some other utility. – Tryer Feb 15 '23 at 01:55
1

@Tryer Yes, it's `jq 'to_entries | sort_by(.key) | from_entries' input.json` – pmf Feb 15 '23 at 08:40

2 Answers2