title: How can I use grep to find a word inside a folder?
body: <p>In Windows, I would have done a search for finding a word inside a folder. Similarly, I want to know if a specific word occurs inside a directory containing many sub-directories and files. My searches for grep syntax shows I must specify the filename, i.e. <code>grep string filename</code>.</p>
  <p>Now, I do not know the filename, so what do I do?
  A friend suggested to do <code>grep -nr string</code>, but I don't know what this means and I got no results with it (there is no response until I issue a <kbd>Ctrl</kbd> + <kbd>C</kbd>).</p>