title: Pause for loop until key is pressed
body: <p>How can I run a for loop which pauses after each iteration until a key is pressed?
  for example, if I wanted to print the line number of file1, file2, file3, but only continuing each after pressing a key:</p>
  
  <pre><code>for f in dir/file? ; do wc -l $f ; pause until key is pressed ; done
  </code></pre>
  
  <p>Apologies if this is trivial, I'm new to the coding.</p>