I have a command that outputs multiple simple json objects like this (for development purposes previously piped to a file foo.txt):
$ cat foo.txt
{"a": "b"}
{"a": "e"}
{"a": "f"}
Now I would like to get it formatted like this:
{
"a": ["b", "e", "f"]
}
I am pretty sure it can be done with jq, but all I can get is the following:
$ cat foo.txt |jq -n '.a |= [inputs]'
{
"a": [
{
"a": "b"
},
{
"a": "e"
},
{
"a": "f"
}
]
}
Any hints?
You were really close. JQ won't extract .a from input objects unless you explicitly state that.
$ jq -n '.a = [inputs.a]' foo.txt
{
"a": [
"b",
"e",
"f"
]
}
inputs.a won't work if I'm not mistaken, inputs is an array and you can't access its properties. [inputs | map(.a)] would work just fine though
inputs is a stream, OP just forgot .a.--slurp, which made inputs empty and raised an error that could be interpreted as trying to index an array with a fieldI would use the following :
jq --slurp --compact-output '{ a: map(.a) }' foo.txt
--slurp makes jq read a sequence of JSON objects as an array of those objects. We map this array of objects to an array of the values of their .a field, and finally return an object which holds this array as its .a field.
You can try it here.
input and inputs. When the goal is to illustrate or encourage best practices, its use should generally be avoided when possible except to highlight its inefficiency.
.aconstant or it could change/dynamic ?ais constant, not changing.