Extract the highest value from a json array using a shell script

Question

Using jq, I extracted a json array from a data source that looks something like this:

[
  {
    "rank": 69,
    "name": "Luigi"
  },
  {
    "rank": 420,
    "name": "Peach"
  },
  {
    "rank": 666,
    "name": "Toad"
  },
  {
    "rank": 42,
    "name": "Mario"
  }
]

Is there an elegant way of extracting the highest value of a field in the array within a shell script? In this example, I'm trying to get "666". I could write a dedicated program to do this easily, but I'd prefer to stay in a single shell script, unless it's too ugly to do that. I'm in the context of an Ubuntu Docker container and can install additional packages if needed.

This works, but only if there are no other numeric values in the array. So it would work with my example but not the real data and the other answers are prettier. Thanks though! — Andreas
– Andreas, Commented Jul 11, 2021 at 17:54

Maks Babarowski · Accepted Answer · 2021-07-12 08:33:59Z

5

With jq, you can use max_by function:

max_by(.rank) will yield:

{
  "rank": 666,
  "name": "Toad"
}

The result can be then piped to extract rank from it: max_by(.rank)|.rank (gives 666). Run this query from terminal by prepending it with jq – jq 'max_by(.rank)|.rank'.

edited Jul 12, 2021 at 8:33

answered Jul 11, 2021 at 17:53

Maks Babarowski

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2 Comments

Andreas Over a year ago

Perfect, just what I was looking for. Very clean, I should've read more about jq, didn't know these functions existed. Thanks!

tink Over a year ago

Thanks for the edit. ;) ... now you have my upvote.

dg428 · Accepted Answer · 2021-07-11 17:52:34Z

1

Assuming the json is in a file called data.json :

cat data.json | jq .[].rank | sort -n -r | head -n 1

answered Jul 11, 2021 at 17:52

dg428

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2 Comments

Jetchisel Over a year ago

No need for the cat really.

Andreas Over a year ago

Thanks, it works, but the other answer is more elegant.

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