NPM安装-G不起任何作用

我正在尝试使用npm在终端中使用以下命令安装gatsbyjs:npm install-g gatsby cli。我得到一个警告和一堆错误:

npm WARN checkPermissions Missing write access to /usr/local/lib/node_modules
npm ERR! path /usr/local/lib/node_modules
npm ERR! code EACCES
npm ERR! errno -13
npm ERR! syscall access
npm ERR! Error: EACCES: permission denied, access '/usr/local/lib/node_modules'
npm ERR!  { Error: EACCES: permission denied, access '/usr/local/lib/node_modules'
npm ERR!   stack: 'Error: EACCES: permission denied, access \'/usr/local/lib/node_modules\'',
npm ERR!   errno: -13,
npm ERR!   code: 'EACCES',
npm ERR!   syscall: 'access',
npm ERR!   path: '/usr/local/lib/node_modules' }
npm ERR! 
npm ERR! Please try running this command again as root/Administrator.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/simanshrestha/.npm/_logs/2018-07-07T22_48_08_615Z-debug.log

我尝试重新安装node.js并使用:npm install npm@latest-g更新npm,但只收到一系列检查权限警告和以下错误:

npm ERR! path /usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri
npm ERR! code EACCES
npm ERR! errno -13
npm ERR! syscall access
npm ERR! Error: EACCES: permission denied, access '/usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri'
npm ERR!  { Error: EACCES: permission denied, access '/usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri'
npm ERR!   stack: 'Error: EACCES: permission denied, access \'/usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri\'',
npm ERR!   errno: -13,
npm ERR!   code: 'EACCES',
npm ERR!   syscall: 'access',
npm ERR!   path: '/usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri' }
npm ERR! 
npm ERR! Please try running this command again as root/Administrator.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/simanshrestha/.npm/_logs/2018-07-07T22_49_59_092Z-debug.log

我一直在尝试修复权限错误,但还是被卡住了(我对这个东西真的很陌生)。

编辑:我不想使用sudo,因为我已经看到它可能会把多个论坛的事情搞砸。