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

Question

I can get the 1st element in a json inside []

$ echo '[{"a":"x", "b":true}, {"a":"XML", "b":false}]' | jq '.[1]' {   "a": "XML",   "b": false } 

But if the json is already disassembled (for instance, after filtering entries using 'select'), how can I choose a single entry and avoid the error seen here?

$ echo '[{"a":"x", "b":true}, {"a":"x", "b":false},{"a":"XML", "b":false}]' | jq '.[] | select( .a == "x")' {   "a": "x",   "b": true } {   "a": "x",   "b": false } $ echo '[{"a":"x", "b":true}, {"a":"x", "b":false},{"a":"XML", "b":false}]' | jq '.[] | select( .a == "x") | .[1]' jq: error (at <stdin>:1): Cannot index object with number 

Answer 1

You can wrap the results from select in an array:

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

Output:

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

Answer 2

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 }