How pack multiline key=value string to array of objects? - json

Question

I have multiline string like
a=aValue
b=bValue
c=cValue
a=dValue
b=eValue
c=fValue
How using jq get json like this?
[
{"a": "aValue", "b": "bValue", "c": "cValue"},
{"a": "dValue", "b": "eValue", "c": "fValue"}
]

Answer 1

Here's an answer that is not tied to the number of distinct keys, and avoids slurping the lines (i.e., has minimal memory requirements):
jq -Rn 'foreach (inputs, null) as $in ({};
if $in == null then .emit = .object
else ($in | capture("(?<key>[^=]*)=(?<value>.*)") // null) as $kv
| if $kv == null
then .
elif (.object | . and has($kv.key))
then .emit = .object | .object = ([$kv]|from_entries)
else .emit = null | .object += ([$kv]|from_entries)
end
end ;
select(.emit).emit )'
The trick here is to use inputs,null so that the "end of file" condition is handled properly.
Note that the above produces a stream, so if you want all the objects in an array, simply enclose the entire jq program in square brackets:
jq -Rn '[ .... ]'

Answer 2

If you don't have any problem with slurping the input, this should do the trick:
jq -R -s '[ split("\n") | map(split("=") | {(.[0]): .[1]}) | _nwise(3) | add ]' file
Online demo
_nwise(n) is an undocumented internal function that given an array emits a stream of subarrays of length n. You can see how it's implemented here. For everything else, see the manual.
If values may contain equals signs, use .[1:] | join("=") instead of .[1].
For a generally-applicable, memory-friendly approach, see peak's answer.