Question 217479 in Json Question posted in
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Json – using jq how can i change the value of a key?

Using jq how can i change the value of a key?
I am trying to change the value of a key based on the length of the key. But it seems to not work as expected.

echo '[{"kiwi": 3 }, {"apple" : 4} ]' | jq 'map(with_entries(.key |= "(.)", .value |= (. | length)))'

actual output:

[
  {
    "kiwi": 3
  },
  {
    "apple": 4
  }
]

desired output –

[
  {
    "kiwi": 4
  },
  {
    "apple": 5
  }
]
Tags:

2

Answers


  1. 0

    Within with_entries, you only need to assign the computed value (.key | length) to .value using =. The value of .key remains unaltered.

    map(with_entries(.value = (.key | length)))

    [
  {
    "kiwi": 4
  },
  {
    "apple": 5
  }
]

    Demo

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  2. 0

    You want

    map( with_entries( .value = ( .key | length ) ) )

    Explanation follows.

    .value |= ( . | length )

    is roughly equivalent to

    .value = ( .value | . | length )

    So you are effectively doing 3 | length and 4 | length. When given a number, length produces the number. So these produce 3 and 4 respectively.

    You want the length of the key.

    .value = ( .key | length )

    Similarly,

    .key |= "(.)"

    can be seen as

    .key = ( .key | "(.)" )

    Since the key is already a string, that’s just

    .key = .key

    And this does nothing at all.

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