Add an optional value to -e

[sfussenegger]

This is the JSON snippet I'm working on (as returned by aws cli):

{
  "Outputs": [
   {
    "OutputValue": "value1",
    "OutputKey": "key1"
   },
   {
    "OutputValue": "value2",
    "OutputKey": "key2"
   }
  ]
}

I want jshon to get the OutputValue where the OutputKey is 'key2'. 'value2' that is. Currently, I don't see a way to do this, so I'd like to suggest an optional value to the -e parameter:

jshon -e Outputs -a -e OutputKey=key2 -p -e OutputValue -u

[vivien]

Is the index reliable jshon -e Outputs -e 1 -e OutputValue -u?

[sfussenegger]

That's what I've used as a workaround for now. It looks like, but since it's not under my control, I can't really rely on it.

[vivien]

True. The problem with your suggestion is that "key=val" is a valid JSON string.

{
 "Outputs": [
  {
   "OutputValue": "value1",
   "OutputKey=key2": "key1"
  },
  {
   "OutputValue": "value2",
   "OutputKey": "key2"
  }
 ]
}

And jshon -e Outputs -e 0 -e OutputKey=key2 gives you "key1".

[sfussenegger]

Yeah, i thought about that, but wasn't sure if it is. If you start escaping things, it gets tricky, not to mention backward compatibility. So maybe precede -e with -s (just like inserting)?

jshon -e Outputs -a -s key2 -e OutputKey -p -e OutputValue -u

Or add an extra flag

jshon -e Outputs -a -e OutputKey -v key2 -p -e OutputValue -u

[keenerd]

Jshon is not really meant to be used that way. It is for safely extracting segments of json information. It can't do anything smart with the data. It passes off the heavy lifting to the standard text-processing tool chain. Generally the form would look something like

.... | jshon -e Outputs -a -e OutputValue -j -p -e OutputKey -j | \
paste -s -d '\t\n' | grep '^"value2"' | cut -f 2

Or a trivial bit of Awk. Since this is a very small and contrived example I can't give you good advice.

[sfussenegger]

Well, I don't see how the suggested features isn't about "safely extracting segments of json". All I suggest is filtering a list of nodes by value instead of key. Admittedly, this might be considered a corner case, but a not too complicated one at that.

Honestly though, I believe that everytime somebody uses awk for JSON or XML processing ... God kills a kitten. Seriously. :)

[vivien]

I prefer the -v approach to extract by value, but using -a is wrong, since a map should return the same amount of object. I'm thinking about a select operator:
-w [<key>] [-v <value>] returning all objects matching key and/or value (no extracting, so no need to rewind).

Given @sfussenegger's example, these calls would be similar:

jshon -e Outputs -a -e OutputValue
jshon -e Outputs -w OutputKey -e OutputValue

and:

jshon -e Outputs -e 1 -e OutputValue
jshon -e Outputs -w OutputKey -v key2 -e OutputValue

So -w would act as a conditional -a ... -p.
It might also be useful to match only by value, with -wv value, didn't think that much about that.

[Napsty]

Good idea. I'd love to see this select (kind of conditional) parameter -w in the future!