title: Sed to replace first forward slash in line after match with a string
body: <p>So I have the following in a file:</p>
  
  <pre><code>/icon.png
  /my/path/tester/icon.png
  /logo.png
  /my/path/tester/logo.png
  </code></pre>
  
  <p>I want to replace all lines that do NOT contain 'tester' and add '/my/path/tester/' to the beginning... leaving:</p>
  
  <pre><code>/my/path/tester/icon.png
  /my/path/tester/icon.png
  /my/path/tester/logo.png
  /my/path/tester/logo.png
  </code></pre>
  
  <p>I would also prefer to edit the file in place using sed.</p>
  
  <p>Thanks in advance!</p>