# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/<(\\/?)\w+:(\w+\\/?) ?(\w+:\w+.*)?>/<$1$2>/g;t' <<< "<?xml version=\"1.0\" encoding=\"utf-8\"?>
<soap:Envelope xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\">
<soap:Body>
<ConnectResponse xmlns=\"aa\">
<ConnectResult xmlns=\"bb\">
<RETURNS>
<STATUS>A92A7EBEE897499fA8B06D5FE94B8A30</STATUS>
<APIPAYLOAD>
<COMMAND>
<TRACKINGID mya=\"cc\">e3d1618b4b7847628b10d4a432ec9151</TRACKINGID>
</COMMAND>
</APIPAYLOAD>
</RETURNS>
</ConnectResult>
</ConnectResponse>
</soap:Body>
</soap:Envelope>"
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