gatsby --version> -bash:gatsby:找不到命令

我使用Mac，并通过以下方式安装了gatsby-cli:

I use mac and I installed gatsby-cli by:

npm install --global gatsby-cli

和'npm root -g'命令打印:

and 'npm root -g' command prints:

/usr/local/lib/node_modules/npm/lib/node_modules

npm成功安装了gatsby，但是， 我无法运行gatsby命令(gatsby --version，gatsby --help) 每当我键入并运行"gatsby --version"时，都会打印:

npm successfully installed gatsby but, I cannot run gatsby command (gatsby --version, gatsby --help) Whenever I type and run "gatsby --version" it prints:

-bash: gatsby: command not found

有什么办法可以解决这个问题?

Is there any way I can fix this problem??