fnva - Fast Environment Version Alter

Fast, cross-platform environment version switcher

中文文档 · Architecture · Releases

fnva is a cross-platform environment switcher for Java, Maven, and Claude Code (CC). Written in Rust, it starts instantly, has zero runtime dependencies, and works via shell snippets without background daemons.

Core Features

• ⚡ Fast & Zero Dependencies: Single static binary.
• 🔄 Session & Global Switching: Per-shell activation and global defaults.
• 🐚 Broad Shell Support: PowerShell, Bash, Zsh, Fish, CMD.
• 🧠 Auto-restore: Opening a new terminal automatically restores your last active environment.
• ☕ Smart Java Management: Scan local JDKs, and automatically download/install version-specific JDKs via Adoptium mirror resolver.
• 📦 Maven Version Management: Query remote versions from mirror directory, auto-install, and switch MAVEN_HOME.
• 🔌 Tool Source Protocol (TSP): Unified abstraction for tool discovery and downloading shared by Java and Maven modules.

Documentation Navigation

• Core Architecture (Chinese)
• Roadmap (Chinese)
• Contributing (Chinese)
• Tool Source Protocol Spec
• Shell Integration Guide
• Terminal Encoding Fix Guide

Installation

One-liner(recommended — auto-configures PATH + shell integration):

# Unix (bash / zsh / fish)
curl -fSsL https://raw.githubusercontent.com/Protagonistss/fnva/main/scripts/install.sh | sh

# Windows (PowerShell)
irm https://raw.githubusercontent.com/Protagonistss/fnva/main/scripts/install.ps1 | iex

Or via a package manager:

npm install -g fnva      # npm
cargo install fnva       # cargo

Or download the binary from Releases and add to PATH.

The curl | sh installer downloads the binary to ~/.fnva/bin and appends a # fnva block(PATH + eval "$(fnva env)")to your shell rc — removable via scripts/uninstall.sh. npm/cargo installs need the shell integration below added manually.

Shell Integration

With shell integration, opening a new terminal restores your last active CC/Java/Maven environments automatically, and fnva <type> use <name> works directly without needing an eval wrapper. See Shell Integration Guide for details.

# Add to your shell profile (bash/zsh):
eval "$(fnva env)"

Quick Start

Java

• Scan local JDKs: fnva java scan
• List remote versions: fnva java ls-remote
• Install a version: fnva java install 17
• List local environments: fnva java list
• Switch version: fnva java use 17 (or eval "$(fnva java use 17)" if shell integration is not installed)
• Set default version: fnva java default 17

Maven

• List remote versions: fnva maven ls-remote
• Install a version: fnva maven install 3.9.16
• List local environments: fnva maven list
• Switch version: fnva maven use 3.9.16 (or eval "$(fnva maven use 3.9.16)" if shell integration is not installed)
• Refresh remote cache: fnva maven refresh

Claude Code (CC)

• List environments: fnva cc list
• Switch environment: fnva cc use mycc (or eval "$(fnva cc use mycc)" if shell integration is not installed)

Configuration

User configuration is stored at ~/.fnva/config.toml (Windows: %USERPROFILE%\.fnva\config.toml).

Uninstall

npm uninstall -g fnva removes the package but does not clean up shell integration: npm v7+ removed postuninstall lifecycle scripts, so fnva cannot hook uninstall. Remove the profile bootstrap line and any stray launchers explicitly — run this before npm uninstall, while the script is still on disk:

node "$(npm root -g)/fnva/scripts/uninstall-shell-integration.js"
npm uninstall -g fnva
rm -rf ~/.fnva   # optional: remove user config/state

For the curl | sh / irm installer, use scripts/uninstall.sh (Unix) or scripts/uninstall.ps1 (Windows) instead.

License

MIT License.