Why are you in my computer?

"Why is this command here? Who installed it?"

why is a CLI tool that identifies the installation source (provider) of a command. It resolves symlinks, checks path patterns, and queries system package managers to tell you if a command is managed by Homebrew, apt, npm, Mise, Flatpak, asdf, SDKMAN!, or simply a system file.

Features

• Provider Identification: Instantly detects if a binary is from Homebrew, apt/dpkg, yum/rpm, zypper/rpm, apk, pacman, Nix, MacPorts, npm, pip, Cargo, Go, etc.
• Symlink Resolution: Traces the "Origin Path" (where your shell finds it) to the "Real Path" (where the binary actually lives).
• System Package Manager Integration: Automatically queries dpkg, rpm/zypper, apk, pacman, or Portage tools for system files to identify the package name.

Installation

Home Manager (Nix)

Add this repository as a flake input:

{
  inputs.why-cli = {
    url = "github:akriaueno/why-cli";
    inputs.nixpkgs.follows = "nixpkgs";
  };
}

Then install it with home.packages:

{ inputs, pkgs, ... }:

{
  home.packages = [
    inputs.why-cli.packages.${pkgs.stdenv.hostPlatform.system}.default
  ];
}

If your Home Manager modules do not already receive inputs, pass them from homeManagerConfiguration with extraSpecialArgs = { inherit inputs; };.

Or import the included Home Manager module:

{ inputs, ... }:

{
  imports = [
    inputs.why-cli.homeManagerModules.default
  ];

  programs.why.enable = true;
}

Homebrew (macOS & Linux) - Recommended

You can easily install why using Homebrew. This method builds the binary from source on your machine, avoiding macOS Gatekeeper warnings.

brew install akriaueno/tap/why

Or, if you prefer to tap the repository first:

brew tap akriaueno/tap
brew install why

Usage

Simply run why followed by the command name.

why <command_name>

Shell Completion

why can print completion scripts for bash, zsh, and fish:

why --completion bash
why --completion zsh
why --completion fish

The generated completion delegates why <TAB> and why l<TAB> to the shell's native command completion instead of invoking why on every tab press.

For one-off bash usage:

source <(why --completion bash)

Examples

1. Version Managers (e.g., Mise, Volta)

It clearly shows which version manager is controlling the command.

$ why node
Command:     node
Provider:    Homebrew
Origin Path: /home/linuxbrew/.linuxbrew/bin/node
Real Path:   /home/linuxbrew/.linuxbrew/Cellar/node/25.2.1/bin/node

2. System Packages (apt/dpkg)

It queries dpkg to find the package name.

 $ why docker
Command:     docker
Provider:    apt/dpkg (docker-ce-cli)
Origin Path: /usr/bin/docker
Real Path:   /usr/bin/docker

3. Flatpak (Smart Fallback)

Even if the command name (e.g., steam) differs from the Flatpak ID, why can find it.

$ why steam
Hint: command 'steam' was not found in PATH, but found 'com.valvesoftware.Steam' in Flatpak.
Command:     steam
Provider:    Flatpak
Origin Path: /var/lib/flatpak/exports/bin/com.valvesoftware.Steam
Real Path:   /var/lib/flatpak/app/com.valvesoftware.Steam/current/active/export/bin/com.valvesoftware.Steam

Supported Providers

why currently supports detection for:

• Package Managers: Homebrew, apt (Debian/Ubuntu), yum/rpm (RHEL/CentOS), zypper/rpm (SUSE), apk (Alpine), pacman (Arch), Portage (Gentoo), MacPorts, Nix, Snap, Flatpak, Scoop, Chocolatey, winget
• Version Managers: Mise, Volta, asdf, SDKMAN!, nvm, fnm, pyenv, rbenv, rvm, Rustup, Conda
• Language Managers: npm (Global), pip/pipx (Python), Cargo (Rust), Go
• System: Standard system paths (/usr/bin, etc.)

Developer

Build from Source

Requirements: Rust toolchain (cargo and rustc).

git clone https://github.com/akriaueno/why-cli.git
cd why-cli
cargo build --release
# The binary is created as './target/release/why'
# Add it to your PATH (e.g., cp target/release/why /usr/local/bin/)

If you change dependencies, run cargo update or cargo generate-lockfile to update Cargo.lock.

Testing

cargo test

License

MIT License.