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
– knittl, Commented Feb 14, 2023 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
– Tryer, Commented Feb 14, 2023 at 16:35

Inian · Accepted Answer · 2023-02-14 16:31:59Z

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, 2023 at 16:31

Inian

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5 Comments

Tryer Over a year ago

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?

Inian Over a year ago

@Tryer jq does a default JSON formatting of the input, which unfortunately it doesn't allow to control for specific fields

peak Over a year ago

re reformatting: see e.g stackoverflow.com/questions/75428312/…

peak Over a year ago

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

Tryer Over a year ago

@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.

peak · Accepted Answer · 2023-02-15 02:25:26Z

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, 2023 at 2:25

answered Feb 14, 2023 at 19:58

peak

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2 Comments

Tryer Over a year ago

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.

pmf Over a year ago

@Tryer Yes, it's jq 'to_entries | sort_by(.key) | from_entries' input.json

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