def shell(command)
      shell_cmd =
        if self["SHELL"]
          flag = self["SHELLFLAG"] || (self["SHELL"] == "cmd" ? "/c" : "-c")
          [self["SHELL"], flag]
        else
          Rscons.get_system_shell
        end
      IO.popen([*shell_cmd, command]) do |io|
        io.read
      end
    end
def shell(command)
      shell_cmd =
        if self["SHELL"]
          flag = self["SHELLFLAG"] || (self["SHELL"] == "cmd" ? "/c" : "-c")
          [self["SHELL"], flag]
        else
          Rscons.get_system_shell
        end
      IO.popen([*shell_cmd, command]) do |io|
        io.read
      end
    end
Execute a command using the system shell.

 The shell is automatically determined but can be overridden by the SHELL
 construction variable. If the SHELL construction variable is specified,
 the flag to pass to the shell is automatically dtermined but can be
 overridden by the SHELLFLAG construction variable.

 @param command [String] Command to execute.

 @return [String] The command's standard output.