title: replace double quotes with back slash double quotes in shell script
body: <p>I am doing 
  P=${P//\"/\\"}</p>
  
  <p>my expectation is</p>
  
  <pre><code>"stackoverflow" is awesome
  </code></pre>
  
  <p>changes to</p>
  
  <pre><code>\"stackoverflow\" is awesome
  </code></pre>
  
  <p>[edit]
  The updated syntax is still not running for</p>
  
  <pre><code>#!/bin/sh
  erroMsg=": Parse Error: line 2:122 mismatched input 'where' expecting EOF near '\"201305%\"'"
  echo $errorMsg
  echo ${errorMsg//\"\\\"}
  echo $errorMsg
  </code></pre>
  
  <p>Output is
     test.sh: 4: test.sh: Bad substitution</p>