Multiple changes to the same file in one run

[tim-kos]

Hey there,

Thank you for an awesome tool! For my use case I need to do multiple small modifications to the same json document and I'd like to do them in one call to the binary.

So for example, instead of:

jj-v1.2.1 -v 500 -O -i my_file.json -o my_file.json bytes_received
jj-v1.2.1 -v 1500 -O -i my_file.json -o my_file.json bytes_expected
jj-v1.2.1 -v 75.62 -O -i my_file.json -o my_file.json upload_duration

I'd like to do something like this:

jj-v1.2.1 -v 500,1500,75.62 -O -i my_file.json -o my_file.json bytes_received,bytes_expected,upload_duration

Reasoning is, less child processes (which are costly in node.js, which I am using) and reading in the same json file only once in Go instead of multiple times (https://github.com/tidwall/jj/blob/master/cmd/jj/main.go#L151) and also saving it only once to disk instead of multiple times (https://github.com/tidwall/jj/blob/master/cmd/jj/main.go#L246).

Is this something that you'd consider implementing, or maybe even accepting a PR for it? 😱

[tidwall]

This is a good idea.

I recommend using standard command line args for each key/value rather than comma-delimited, because there's the possibility that commas are a part of the JSON key it's associated value, and we should avoid any additional escaping.

jj -v 500 -v 1500 -v 75.62 -O -i my_file.json -o my_file.json bytes_received bytes_expected upload_duration

This way the jj command will recognize that there are three updates occuring to the JSON file and expect three keys.

How does this sound?

[Acconut]

Good propasal, @tidwall. What should happen if someone if trying to updates multiple properties via stdin/file and does not supply the values using -v? Should that be prohibited?

[tidwall]

Yeah. I think that should be prohibited. Multiple keys for update/set operations only. Unless we want to accept multiple keys for a get operations and return the values as a JSON array.

[nick-bull]

Temporary solution - edit for your requirements:

jj_v() {
 __val="$1";
 __key="$2";
 jj -v "$__val" "$__key" | (test -n "$3" && f "${@:3}" || cat)
}

echo '{"name":{"last":"Smith"}}' | jj_v Andy name.first Dandy name.middle outputs:

{
  "name": {
    "middle": "Dandy",
    "first": "Andy",
    "last": "Smith"
  }
}