Android: Requesting root access in your app

转帖：http://www.stealthcopter.com/blog/2010/01/android-requesting-root-access-in-your-app/
This snippet shows how root access can be requested inside an application in order to write a file into a place we do not have permission to access usually. Requesting root access will only work if your phone allows it, or it has been ‘rooted’ (hacked to allow superuser permissions).
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Process p;   
try {   
   // Preform su to get root privledges   
   p = Runtime.getRuntime().exec("su");    
  
   // Attempt to write a file to a root-only   
   DataOutputStream os = new DataOutputStream(p.getOutputStream());   
   os.writeBytes("echo \"Do I have root?\" >/system/sd/temporary.txt\n");   
  
   // Close the terminal   
   os.writeBytes("exit\n");   
   os.flush();   
   try {   
      p.waitFor();   
           if (p.exitValue() != 255) {   
              // TODO Code to run on success   
              toastMessage("root");   
           }   
           else {   
              &nb