JQ - format JSON array appending values to a specific a value

Question

I am trying to get this:

[   
    ["John Black",[ 
        ["Lorem ipsum dolor sit amet.",27], 
        ["Ut tempus lectus ut mi.",23]
    ]],
    ["Peter Pan",[ 
        ["Quisque pulvinar odio.",22],
        ["Nec ut lorem quis interdum elit.",32]
    ]],
    ["Gary Halbert",[ 
        ["Placerat aliquam.",17]
    ]],
    ["Richard Gere",[ 
        ["Porttitor commodo fermentum.",28]
    ]]
]

Till now, this is what I got:

export A=$(cat <<'EOL'
[
["John Black",["Lorem ipsum dolor sit amet.",27]],
["Peter Pan",["Quisque pulvinar odio.",22]],
["John Black",["Ut tempus lectus ut mi.",23]],
["Gary Halbert",["Placerat aliquam.",17]],
["Peter Pan",["Nec ut lorem quis interdum elit.",32]],
["Richard Gere",["Porttitor commodo fermentum.",28]]
]
EOL
)
echo "$A" | jq 'map({(.[0]): .[1]}) | add'

Resulting this:

{
  "John Black": [
    "Ut tempus lectus ut mi.",
    23
  ],
  "Peter Pan": [
    "Nec ut lorem quis interdum elit.",
    32
  ],
  "Gary Halbert": [
    "Placerat aliquam.",
    17
  ],
  "Richard Gere": [
    "Porttitor commodo fermentum.",
    28
  ]
}

I am using jq-1.5. Any ideas? Thanks.

Aside: export is utterly unneeded here; it's using a limited resource unnecessarily (environment variables are stored in the same space used for the argument vector, so when you export a shell variable you're decreasing your maximum command-line length for all subprocesses of that shell). — Charles Duffy
– Charles Duffy, Commented Mar 6, 2017 at 21:11
Man, where did you learn that? If that was a book, please, I want that too... — Roger
– Roger, Commented Mar 6, 2017 at 22:46

Charles Duffy · Accepted Answer · 2017-03-06 21:24:43Z

2

This is an appropriate use case for a reducer. Most of the below is related not to joining items under shared keys, but to getting them into the desired nested-list form:

jq -n '[
  inputs |
  reduce .[] as $item ({}; .[$item[0]] += [$item[1]]) |
  to_entries |
  .[] |
  [.key, .value]
]' <<<"$A"

...yields as output (edited only for compactness with regard to whitespace):

[
  ["John Black", [["Lorem ipsum dolor sit amet.", 27], ["Ut tempus lectus ut mi.",23]]],
  ["Peter Pan", [["Quisque pulvinar odio.",22], ["Nec ut lorem quis interdum elit.", 32]]],
  ["Gary Halbert", [["Placerat aliquam.", 17]]],
  ["Richard Gere", [["Porttitor commodo fermentum.", 28]]]
]

edited Mar 6, 2017 at 21:24

answered Mar 6, 2017 at 21:17

Charles Duffy

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2 Comments

Roger Over a year ago

If there is a book or a course about this, I want to know!

mklement0 Over a year ago

@Roger: You won't find such advanced techniques in the tutorial, but the manual covers everything - albeit in a condensed form that may not make the possibilities obvious. The manual does have examples, however, and there's also an online playground. Finally, there are plenty of excellent answers on SO already (this one definitely qualifies).

Gabriel Mancini · Accepted Answer · 2017-03-06 19:23:20Z

0

the Couchdb engine is append only, it means that each document will append into a file manager by Couchdb, and each file is related to a db.

to use properly think how to avoid updates in the same document, remember all revisions will be storage.

my suggestion for each document.

{
  "name": "John Black",
  "entries": [
    {
      "test": "Lorem ipsum dolor sit amet.",
      "value": 27
    }, 
    {
       "text": "Ut tempus lectus ut mi.",
       "value": 23
    }
  ],
  "type": "user"
}

answered Mar 6, 2017 at 19:23

Gabriel Mancini

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4 Comments

Roger Over a year ago

So, with CouchDB, if I need to add other quotes to an author I will have to read the JSON object/array, make the addition and overwrite the entire document?

Gabriel Mancini Over a year ago

yes and this will generate a revision, which is a copy of the document.

Charles Duffy Over a year ago

Did a prior rev of the question reference CouchDB? (As the current version asks only about jq, I'm curious to see this here).

Roger Over a year ago

The question was too large so I edited it. As far as I could see, I did not had too much to gain, in my case, working with CouchDB. Indeed, I decided it would be quicker to save the JSON array into a gunziped text file and read it back JQ to further editions.

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