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randusername • yesterday at 3:46 PM • 4 replies • view on HN

I'm not GP, I use jq all the time, but I each time I use it I feel like I'm still a beginner because I don't get where I want to go on the first several attempts. Great tool, but IMO it is more intuitive to JSON people that want a CLI tool than CLI people that want a JSON tool. In other words, I have my own preconceptions about how piping should work on the whole thing, not iterating, and it always trips me up.

Here's an example of my white whale, converting JSON arrays to TSV.

cat input.json | jq -S '(first|keys | map({key: ., value: .}) | from_entries), (.[])' | jq -r '[.[]] | @tsv' > out.tsv

Replies

nh23423fefe • yesterday at 6:55 PM

    <input.json  jq -S  -r '(first | keys) , (.[]| [.[]]) | @tsv'
    <input.json  # redir
    jq
    -S           # sort
    -r           # raw string out
    '
    (first | keys) # header
    ,              # comma is generator
    (.[] |           # loop input array and bind to .
    [                # construct array
     .[]             # with items being the array of values of the bound object
     ])           
     | @tsv'        # generator binds the above array to . and renders to tsv
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figmert • yesterday at 5:39 PM

Here's an easier to understand query for what you're trying to do (at least it's easier to understand for me):

    cat input.json | jq -r '(first | keys) as $cols | $cols, (.[] | [.[$cols[]]]) | @tsv'
That whole map and from entries throws it off. It's not a good use for what you're doing. tsv expects a bunch of arrays, whereas you're getting a bunch of objects (with the header also being one) and then converting them to arrays. That is an unnecessary step and makes it a little harder to understand.
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lokar • yesterday at 4:39 PM

I find it much harder to remember / use each time then awk

firesteelrain • yesterday at 10:54 PM

Trying to make a generic pipeline for json arrays because you don’t know the field names?