code: public static String getUserShell()
          throws EnvironmentException
      {
          if( isMacOsX() )
          {
              return getMacUserShell();
          }
  
          if( isWindows() )
          {
              return getWindowsUserShell();
          }
  
          if( isUnix() )
          {
              return getUnixUserShell();
          }
  
          String message = "Environment operations not supported on unrecognized operatings system";
          UnsupportedOperationException cause = new UnsupportedOperationException( message );
          throw new EnvironmentException( cause );
      }
docs: Gets the user's shell executable.
  
  @return the shell executable for the user
  
  @throws EnvironmentException the there is a problem accessing shell
  information