title: why webdriver-update command not found although protractor is installed ?
body: <p>why webdriver-update command not found although protractor is installed ?  </p>
  
  <p>i installed protractor node as</p>
  
  <pre><code>sudo npm install protractor -g
  </code></pre>
  
  <p>and when i try to make</p>
  
  <pre><code>sudo webdriver-manager update
  </code></pre>
  
  <p>it return with  </p>
  
  <pre><code>sudo: webdriver-manager: command not found
  </code></pre>
  
  <p>i tried also to install it manually but i failed to do.</p>
  
  <pre><code>tamer@tamer-Inspiron-N5110:/media/tamer/Work/conFusion/test$ protractor protractor.conf.js
  [15:23:48] I/direct - Using ChromeDriver directly...
  [15:23:48] I/launcher - Running 1 instances of WebDriver
  [15:23:48] E/direct - Error code: 135
  [15:23:48] E/direct - Error message: Could not find chromedriver at /home/tamer/.npm-global/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/chromedriver_2.22
  [15:23:48] E/direct - Error: Could not find chromedriver at /home/tamer/.npm-global/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/chromedriver_2.22
      at Direct.getNewDriver (/home/tamer/.npm-global/lib/node_modules/protractor/built/driverProviders/direct.js:65:27)
      at Runner.createBrowser (/home/tamer/.npm-global/lib/node_modules/protractor/built/runner.js:198:43)
      at /home/tamer/.npm-global/lib/node_modules/protractor/built/runner.js:277:30
      at _fulfilled (/home/tamer/.npm-global/lib/node_modules/protractor/node_modules/q/q.js:834:54)
      at self.promiseDispatch.done (/home/tamer/.npm-global/lib/node_modules/protractor/node_modules/q/q.js:863:30)
      at Promise.promise.promiseDispatch (/home/tamer/.npm-global/lib/node_modules/protractor/node_modules/q/q.js:796:13)
      at /home/tamer/.npm-global/lib/node_modules/protractor/node_modules/q/q.js:556:49
      at runSingle (/home/tamer/.npm-global/lib/node_modules/protractor/node_modules/q/q.js:137:13)
      at flush (/home/tamer/.npm-global/lib/node_modules/protractor/node_modules/q/q.js:125:13)
      at nextTickCallbackWith0Args (node.js:420:9)
  [15:23:48] E/launcher - Process exited with error code 135
  tamer@tamer-Inspiron-N5110:/media/tamer/Work/conFusion/test$ sudo webdriver-manager update
  [sudo] password for tamer: 
  sudo: webdriver-manager: command not found
  </code></pre>