Getting output using jq - json

Question

I have the following JSON outp
{
"environment": {
"reg": "abc"
},
"system": {
"svcs": {
"upsvcs": [
{
"name": "monitor",
"tags": [],
"vmnts": [],
"label": "upsvcs",
"credentials": {
"Date": "Feb152018",
"time": "1330"
}
},
{
"name": "application",
"tags": [],
"vmnts": [],
"label": "upsvcs",
"credentials": {
"lastViewed": "2018-02-07"
}
}
]
}
}
and to retrieve Date value (from credentials). I have tried `curl xxx | jq -r '. | select (.Date)'
which is not returning any value. Can someone please let me know what is the correct syntax and any explanation on how to retrieve elements (or any articles that do so).
TIA

Answer 1

The (or at least a) short answer is:
.system.svcs.upsvcs[0].credentials.Date
Without a schema, it is often a bit tricky to get the exact path correctly, so you might want to consider using the jq filter paths. In your case:
$ jq -c paths input.json | grep Date
["system","svcs","upsvcs",0,"credentials","Date"]
You could also use this path (i.e., the above array) directly:
$ jq 'getpath(["system","svcs","upsvcs",0,"credentials","Date"])' input.json
"Feb152018"
and thus you could use a "path-free" query:
$ jq --argjson p $(jq -c paths input.json | grep --max 1 Date) 'getpath($p)' input.json
"Feb152018"
Another approach would be just to retrieve all “truthy” .Date values, no matter where they appear:
$ jq -c '.. | .Date? // empty' input.json
"Feb152018"
select
Since you mentioned select, please note that:
$ jq -c '.. | select(.Date?)' input.json
{"Date":"Feb152018","time":"1330"}
Further information
For further information about jq in general and the topic of retrieval in particular, see the online tutorial, manual, and FAQ:
https://stedolan.github.io/jq/tutorial/
https://stedolan.github.io/jq/manual/v1.5/
https://github.com/stedolan/jq/wiki/FAQ