jq++

A project that productizes the jq-front. jq-front is a simple utility that extends JSON files with file- and node-level inheritance and expression evaluation, making it easier to create reusable and dynamic JSON-based configurations.

This project follows the standard Go project layout.

Installation

Prerequisites

• Go 1.24.5 or later (see go.mod for the exact version requirement)
• Make (optional, for using the Makefile)

Download a prebuilt binary

Each release attaches prebuilt binaries for common platforms. Grab the one for your OS/arch from the Releases page, rename it to jq++, chmod +x it, and put it on your PATH.

Install from Source

The easiest way to install jqplusplus is using go install:

go install github.com/dakusui/jqplusplus/cmd/jqplusplus@latest && jqplusplus

This will install the jqp++ binary to $GOPATH/bin or $GOBIN (if set). Make sure this directory is in your PATH.

Build from Source

Clone the repository:

git clone https://github.com/dakusui/jqplusplus.git
cd jqplusplus

Then build using Make:

make build

This will create the executable as bin/jq++.

Alternatively, build directly with Go:

go build -o bin/jq++ ./cmd/jqplusplus

Adding to PATH

After building, you can add the bin directory to your PATH, or copy the binary to a directory already in your PATH:

# Option 1: Add bin directory to PATH (add to ~/.bashrc, ~/.zshrc, etc.)
export PATH="$PATH:$(pwd)/bin"

# Option 2: Copy to a directory in PATH (e.g., /usr/local/bin)
sudo cp bin/jq++ /usr/local/bin/

Usage Example

Let's prepare files, name.json and greeting.json, from which you want to create a new JSON by extending them.

$ echo '{"yourname":"Mark"}' > name.json
$ cat name.json
{"yourname":"Mark"}

$ echo '{"greeting":"Hello"}' > greeting.json
$ cat greeting.json
{"greeting":"Hello"}

Then create a file that extends them.

$ echo '{
    "$extends": ["greeting.json", "name.json"],
    "sayHello": "eval:string:refexpr(\".greeting\") + \", \" + refexpr(\".yourname\") + \". Today is \" + (now|todate) + \". How are you doing?\""
  }' > sayHello.json

Now, let's try jq++.

$ jq++ sayHello.json
{
  "yourname": "Mark",
  "greeting": "Hello",
  "sayHello": "Hello, Mark. Today is 2026-03-21T17:57:25Z. How are you doing?"
}
$

Doesn't it seem useful? Have fun!

Reading from stdin

If no files are given, jq++ reads from stdin. Stdin has no filename, so it is parsed as JSON by default. To feed YAML (or any other supported format) via stdin, tell jq++ the type with -t / --input:

$ echo 'greeting: Hello' | jq++ --input yaml
{
  "greeting": "Hello"
}

$ echo 'greeting: Hello' | jq++ -t yaml   # short form; -t=yaml also works

Supported types match the recognized file extensions: json, yaml/yml, toml, json5, hocon/conf, and their ++ variants. The flag only applies to stdin — input from files is detected by its extension, so passing -t together with file arguments is an error.

YAML in, YAML out with yq++

yq++ is a YAML front-end for jq++: it runs jq++, strips private _-prefixed holder keys, and emits YAML. Because its job is YAML, stdin is treated as YAML by default (no -t needed):

$ yq++ config.yaml++          # resolve a YAML file, emit YAML
$ yq++ < config.yaml          # same, from stdin

yq++ requires jq, plus either ruby or python3 (with PyYAML) to emit YAML.

Project Structure

• cmd/jqplusplus/main.go: Application entry point
• internal/: Private application and library code
• pkg/: Public libraries (if any)
• go.mod, LICENSE, README.md, Makefile: Project metadata and configuration

Building and Running

To build the main application:

make build

This will create the executable as bin/jq++.

To run the program:

./bin/jq++

Or run directly without building:

make run

Project Dependencies

• xmllint: On Ubuntu, do sudo apt install libxml2-utils