First occurrence of element in json dictionary with jq

Question

I have following json :

$ echo '{ "format_id": "250" }{ "format_id": "18" }{ "format_id": "140" }{ "format_id": "18" }{ "format_id": "244" }' | jq .
{
  "format_id": "250"
}
{
  "format_id": "18"
}
{
  "format_id": "140"
}
{
  "format_id": "18"
}
{
  "format_id": "244"
}

I managed to extract the format_ids for which it equals to "18" :

$ echo '{ "format_id": "250" }{ "format_id": "18" }{ "format_id": "140" }{ "format_id": "18" }{ "format_id": "244" }' | jq -r 'select(.format_id=="18")'
{
  "format_id": "18"
}
{
  "format_id": "18"
}

I want to extract out of that the 1st occurrence of format_id.

So I tried the solutions given here but none of them worked because I guess they need to be adapted to my input data somehow :

$ echo '{ "format_id": "18" }{ "format_id": "18" }' | jq '[.[]|select(.format_id)][0]'
jq: error (at <stdin>:1): Cannot index string with string "format_id"
jq: error (at <stdin>:1): Cannot index string with string "format_id"
$ echo '{ "format_id": "18" }{ "format_id": "18" }' | jq '( map(select(.format_id)) | first  )'
jq: error (at <stdin>:1): Cannot index string with string "format_id"
jq: error (at <stdin>:1): Cannot index string with string "format_id"
$ echo '{ "format_id": "18" }{ "format_id": "18" }' | jq '( first(.[]  | select(.format_id)) )'
jq: error (at <stdin>:1): Cannot index string with string "format_id"
jq: error (at <stdin>:1): Cannot index string with string "format_id"
$ echo '{ "format_id": "18" }{ "format_id": "18" }' | jq 'map(select(.format_id))|.[0]'        
jq: error (at <stdin>:1): Cannot index string with string "format_id"
jq: error (at <stdin>:1): Cannot index string with string "format_id"

Can you please help me ?

Answer 1

If your jq has inputs then it would be best to use it in conjunction with the -n command-line option and the following jq filter:

first(inputs | select(.format_id =="18"))

If your jq does not have inputs

... then you'd have to use the -s command-line option, e.g. with the following filter:

first(.[] | select(.format_id =="18"))

Here, using inputs is preferable as it requires less RAM.