Package manager

When you will meet it

The first line of every AI tool's install guide is one of these: npm install -g, pip install, brew install. Knowing that all three mean the same kind of thing stops you copying the wrong ecosystem and lets you track down where a tool actually landed.

Minimal example

brew install python                          # macOS / Linux：系統層級的工具
npm install -g @anthropic-ai/claude-code     # 全域裝一個 Node.js 命令列工具
python3 -m pip install requests              # 裝一個 Python 套件

All three lines install a package, but into three different places for three different kinds of program. The first word of the command tells you which ecosystem you are standing in.

What people get wrong

• Reacting to command not found by reinstalling with a different package manager. A tool belongs to one ecosystem; using another just leaves you with a second useless copy.
• Assuming a global install (npm install -g) and a project install (npm install) are the same. The first puts a command anywhere on your machine can reach; the second puts packages only inside the current project folder.