title: How to encode protocol buffer string to binary using protoc
body: <p>I been trying to encode strings using protoc cli utility.
  Noticed that output still contains plain text.
  What am i doing wrong?</p>
  
  <pre><code>osboxes@osboxes:~/proto/bin$ cat ./teststring.proto
  syntax = "proto2";
  message Test2 {
    optional string b = 2;
  }
  
  echo b:\"my_testing_string\"|./protoc --encode Test2 teststring.proto&gt;result.out
  </code></pre>
  
  <p>result.out contains:</p>
  
  <pre><code>^R^Qmy_testing_string
  </code></pre>
  
  <p>protoc versions libprotoc 3.6.0 and libprotoc 2.5.0</p>