title: How to write string with octal value
body: <p>In bash, I would like to write the string <code>"BLA\1"</code>
  so it will be a buffer <code>42 4C 41 01</code> but the result is <code>42 4C 41 5C 31</code></p>
  
  <p>To complete, in python if you write <code>"BLA\1"</code> in a binary file, the <code>"\1"</code> is interpreted as <code>"1"</code></p>
  
  <p>So how can I write the string <code>"BLA\1"</code> correctly in bash? </p>