Select nth element from multidimensional JSON array with jq

Question

How can I use jq to transform this array of arrays:

[
  [
    "sequence",
    "int"
  ],
  [
    "time",
    "string"
  ],
  ...
]

Into an array that contains the first (0) element from every subarray? Meaning to produce output like this:

[
    "sequence",
    "time",
    ...
]

I was thinking to use reduce xx as $item (...) but I didnt manage to come up with anything useful.

I tried to tag as jq, but now i see that if you do that, SO changes the tag to jquery... you cant actually tag something jq — Dreen, Sep 17 '13 at 12:45
@Dreen - For future reference, since [`jq` is defined as a synonym for `jquery`](http://stackoverflow.com/tags/jquery/synonyms) in Stack Overflow's tag system, it gets changed when you submit the question. I don't have the rights to undo this (@SomeoneReadingThisWhoDoesHaveThisPrivilege - I think it could be done, as the `jq` synonym has never been used) I have fixed you up with a brand new `jq-json-processor` tag instead. — Mathijs Flietstra, Sep 19 '13 at 14:45

score 5 · Accepted Answer · answered Sep 19 '13 at 09:16

5

You can use map filter this way:

jq 'map(.[0])'

answered Sep 19 '13 at 09:16

Psylone

Now, how to apply string interpolation on the result? – ccpizza Oct 15 '17 at 16:15

score 1 · Answer 2 · edited Sep 15 '16 at 19:56

1

Another option would be jq '[.[][0]]'

this gives the same result as using map(.[0])

edited Sep 15 '16 at 19:56

Buddy

answered Sep 15 '16 at 19:53

rdm

score 0 · Answer 3 · answered Aug 02 '17 at 07:18

0

Here is a solution using reduce

reduce .[] as $k ( null; . + [$k[0]] )

answered Aug 02 '17 at 07:18

jq170727

3 Answers3