====== jq ======

**[[https://stedolan.github.io/jq/|jq]]** a lightweight and flexible command-line JSON processor.


  * Le [[https://stedolan.github.io/jq/manual/|Manuel]]
  * La [[https://github.com/stedolan/jq/wiki/FAQ|FAQ]]
  * Le [[https://github.com/stedolan/jq/wiki/Cookbook|Cookbook]]

  * Pour faire des requêtes en ligne : https://jqplay.org

  * [[https://kaijento.github.io/2017/03/20/json-parsing-jq-group_by-max_by-and-sort_by/|JSON parsing: jq group_by() max_by() sort_by()]]
  * [[https://gist.github.com/olih/f7437fb6962fb3ee9fe95bda8d2c8fa4|Processing JSON using jq]]
  * [[https://stackoverflow.com/questions/tagged/jq|jq sur stackoverflow]] 


===== Play with jq =====

''members.json'':
<code>
[
 {
  "member_id": 123,
  "loans":[
   {
    "date": "123",
    "media": [
     { "title": "foo" },
     { "title": "bar" }
    ]
   },
   {
    "date": "456",
    "media": [
     { "title": "foo" }
    ]
   }
  ]
 },
 {
  "member_id": 456,
  "loans":[
   {
    "date": "789",
    "media": [
     { "title": "foo"}
    ]
   }
  ]
 }
]
</code>

==== Howto count occurrence of "grouped by key=value" with jq? ====

https://stackoverflow.com/questions/69423726/howto-count-occurrence-of-grouped-by-key-with-jq/

=== Sans group_by ===

<code bash>
jq '"foo" as $title | .[] | {
  id: .member_id,
  $title,
  count: [.loans[].media[] | select(.title == $title)] | length
}' members.json
</code>
<code>
{
  "id": 123,
  "title": "foo",
  "count": 2
}
{
  "id": 456,
  "title": "foo",
  "count": 1
}
</code>

=== Avec group_by ===

<code bash>
jq  'map(
         (.member_id) as $m
        | .loans[].media[]
        | select(.title=="foo")
        | {id: $m, title: .title}
        )
    |group_by(.id)[]
    |.[0] + { count: length }
' members.json
</code>