Node.js exception 201 when running azure on mac os

I just installed windows azure sdk following the instruction in http://www.windowsazure.com/en-us/manage/linux/how-to-guides/command-line-tools/.

Afte the installation, I run the command "azure account download" as instructed, but I got the below error:

node.js:201

    throw e; // process.nextTick error, or 'error' event on first tick
          ^

Error: Cannot find module 'azure'

at Function._resolveFilename (module.js:332:11)
at Function._load (module.js:279:25)
at Module.require (module.js:354:17)
at require (module.js:370:17)
at Object.<anonymous> (/usr/local/azure/lib/utils.js:21:13)
at Module._compile (module.js:441:26)
at Object..js (module.js:459:10)
at Module.load (module.js:348:31)
at Function._load (module.js:308:12)
at Module.require (module.js:354:17)

It seems that node.js cannot find the azure module. I am new to both node.js and azure, and could you anyone give me some suggestions on this error? Thanks!