get the first (or n'th) element in a jq json parsing

You can wrap the results from select in an array:

jq '[.[]|select(.a=="x")][0]' your.json

Output:

{
  "a": "x",
  "b": false
}

jq also provides first/0, last/0, nth/1 so in this case the filter

  ( map(select(.a == "x")) | first  )
, ( map(select(.a == "x")) | last   ) 
, ( map(select(.a == "x")) | nth(1) )

produces

{
  "a": "x",
  "b": true
}
{
  "a": "x",
  "b": false
}
{
  "a": "x",
  "b": false
}

Additional streaming forms 'first/1', 'last/1' and 'nth/2' are also available so with this data

  ( first(.[]  | select(.a == "x")) )   
, ( last(.[]   | select(.a == "x")) )
, ( nth(1; .[] | select(.a == "x")) )

produces

{
  "a": "x",
  "b": true
}
{
  "a": "x",
  "b": false
}
{
  "a": "x",
  "b": false
}

use map

cat raw.json|jq -r -c 'map(select(.a=="x"))|.[1]'

map recivce a filter to filter an array.

this command

cat raw.json|jq -r -c 'map(select(.a=="x"))'

give the middle result

[{"a":"x","b":true},{"a":"x","b":false}]

.[1] take the first element

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