For example if we have a file that contains JSON object like
{"a": 1, "b":{"c": 11}{"a": 2, "b":{"c": 22}}{"a": 3, "b":{"c": 33}}
And you want to construct something like
["1", "11"]["2", "22"]["3", "33"]
You can do that with jq
$ cat filename.json | jq -c '[.a, .b.c]'
this is particularly usefull to grep something from JSON log