How to count items in JSON object using command line?

Question

I'm getting this kind of JSON reply from a curl command:

[
  {
    "cid": 49,
    "pyn": "yi4",
    "hans": "亿",
    "hant": "億",
    "tid": 68,
    "l10n": "cent million",
    "pid": 1,
    "pos": "num",
    "pos_txt": ""
  },
  {
    "cid": 50,
    "pyn": "yi4",
    "hans": "亿",
    "hant": "億",
    "tid": 69,
    "l10n": "100 millions",
    "pid": 1,
    "pos": "num",
    "pos_txt": ""
  }
]

How can I count the number of items in the array (here 2), using Bash or a command line (e.g. underscore) ?

Is JavaScript solution, okay for you? – thefourtheye Jan 24 '14 at 13:51 — thefourtheye, Jan 24 '14 at 13:51
Through `NPM` module yes. Otherwise, no. – Édouard Lopez Jan 24 '14 at 13:53 — Édouard Lopez, Jan 24 '14 at 13:53
Check my solution. That needs no npm. Plain JavaScript. – thefourtheye Jan 24 '14 at 13:55 — thefourtheye, Jan 24 '14 at 13:55
I'm in a bash context, not web – Édouard Lopez Jan 24 '14 at 13:59 — Édouard Lopez, Jan 24 '14 at 13:59

score 627 · Accepted Answer · edited Sep 25 '18 at 19:59

627

Just throwing another solution in the mix...

Try jq, a lightweight and flexible command-line JSON processor:

jq length /tmp/test.json

Prints the length of the array of objects.

edited Sep 25 '18 at 19:59

peak

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answered Jan 25 '14 at 19:50

Ken

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4

Your initial `jq` code (`.[]`) return the length of each `object` in the root array, while I'm looking for the length of the root array itself. Need to fix to `.` – Édouard Lopez Jan 26 '14 at 09:52
53

If your root is not an array but an object with a key that contains an array, i.e. { "key": [elem1, elem2] } , then you can use use `jq '.[] | length' file.json` – Alex Bitek Jan 27 '15 at 15:10
2

Another useful option for that @MnemonicFlow is `jq map_values(length) file.json` . That will give you the keys as well. – Paulo Casaretto Dec 09 '16 at 19:06
17

And if your input is made of independent objects instead of a single array, you'd use the `-s` or `--slurp` option, which collects them into an array while reading: `jq -s length file.json` – hemflit Jul 02 '18 at 10:34
`. | ` is not required, `jq 'length' ... ` is enough – ssc Sep 02 '18 at 14:39
@bitek Either I understood you wrong, or you're mistaken. `echo '{"key":[1,"asdf"]}' | jq '.[] | length'` gives an error. What produces expected result to me is `echo '{"key":[1,"asdf"]}' | jq '.key | length'`. – x-yuri Sep 30 '18 at 01:39
Bitek's method (`.[]`) works for me but it's just a shorthand for `.key`, usable when the object is only a wrapper around an array (in which case the key is basically arbitrary). – Sinjai Jun 23 '22 at 04:31

score 87 · Answer 2 · edited Jul 16 '21 at 17:47

87

You can also use jq to track down the array within the returned json and then pipe that in to a second jq call to get its length. Suppose it was in a property called records, like {"records":[...]}.

$ curl https://my-source-of-json.com/list | jq -r '.records | length'
2
$

edited Jul 16 '21 at 17:47

Mr. Lance E Sloan

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answered Sep 21 '20 at 19:23

yuvilio

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score 86 · Answer 3 · edited Mar 31 '16 at 11:21

86

The shortest expression is

curl 'http://…' | jq length

edited Mar 31 '16 at 11:21

Édouard Lopez

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answered Mar 31 '16 at 10:21

nikolay

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score 19 · Answer 4 · answered Aug 24 '21 at 07:10

If the JSON is being read from a file, try this -

number_of_objects=`jq '. | length' json_file_name.json`
echo $number_of_objects

If the JSON array is inside a key in the JSON as shown below -

{
  "fruits": [
    "apples",
    "oranges",
    "pears"
  ]
}

try this -

number_of_objects=`jq '.fruits | length' json_file_name.json`
echo $number_of_objects

(You'll have to download jq for this solution to work)

score 6 · Answer 5 · answered Feb 21 '23 at 20:42

6

Assume this structure:

(stored in a variable named json)

{
    "results": [
        { "id": 1 }
        { "id": 2 }
    ]

}

If you're looking to count how many are in the results array, the command is:

$json | jq '.results | length'

answered Feb 21 '23 at 20:42

Kellen Stuart

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score 5 · Answer 6 · answered Jan 24 '14 at 14:45

5

A simple solution is to install jshon library :

jshon -l < /tmp/test.json
2

answered Jan 24 '14 at 14:45

Édouard Lopez

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score 3 · Answer 7 · edited Aug 16 '23 at 22:00

3

try qic. it works like jq/jello. qic support interactive mode as well.

cat test.json | qic "len(_)"

https://walkerever.github.io/qic/

edited Aug 16 '23 at 22:00

Benjamin Loison

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answered Jul 07 '21 at 00:40

Y W

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How to count items in JSON object using command line?

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