# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/<([^>\s]+)[^>]*>(?:\s*(?:<br \\/>| | | | | | | )\s*)*<\\/\1>//gm;t' <<< "<div>
<h1>This is a html structure.</h1>
<p>This is not empty.</p>
<p></p>
<p><br /></p>
<p> <br />  </p>
<p> </p>
<p> </p>
</div>"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html