# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/<([^ ]*)[^=]*?={([^}]*?)}>([^<]*)<\\/\1>\s*/<!-- $2 -->$3/g;t' <<< "<section className={CLASS_A}>
Un-touched stuff here
</section>
<hr />
<section className={CLASS_B}>
Un-touched stuff here
</section>"
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