title: Find & Replace String in All Found Files with LaTeX $sim$ -> $\sim$
body: <p>I know this sort of question has been asked many times before, but I'm running into an odd circumstance where my feeble brain forgot to include a <code>\</code> while calling <code>$\sim$</code> in some markdown files. I need to go through and replace all instances of <code>$sim$</code> with <code>$\sim$</code>. My code is running but not actually replacing any of the words that I want. Here are some variations I have tried:</p>
  
  <pre><code>grep -rl '\$sim\$' . | xargs sed -i 's/\$sim\$/$\sim$/g'
  
  grep -rlF '$sim$' . | xargs sed -i 's/\$sim\$/$\sim$/g'
  
  grep -rlF '$sim$' . | xargs sed -i 's/$sim$/$\sim$/g'
  
  grep -rlF '$sim$' . | xargs sed -i '' -e 's/$sim$/$\sim$/g'
  </code></pre>
  
  <p>And other odd variations on a theme. The code just runs with no output but when I check the files nothing has changed. I figure this is either a <code>sed</code> issue (I'm macOS) or a regex issue. </p>