title: grep find lines that contains " \t"
body: <p>I was requested to make a shell script to check for simple mistakes in files.
  I wanted to find, for each line if</p>
  
  <p>(regex:) "[ ]\t" ever happens.</p>
  
  <p>The problem is that grep is ignoring the \ and is taking "t" as a literal. I also tried writting the characters themselves in a file and asking grep to read it but it didn't work.
  Is there a way to find for the regex " \t" in files using any of the usual linux tools (like grep)?</p>
  
  <p>I already tried:</p>
  
  <pre><code>grep -E --ignore-case --line-number --with-filename --file="b" file
  </code></pre>
  
  <p>(b contains: "  ")
  and also:</p>
  
  <pre><code>grep -E --ignore-case --line-number --with-filename --regexp=" [\t]" file
  </code></pre>