# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(http(s)?:[\/]{2})?([a-z0-9][a-z0-9\-]+.)+([a-z0-9\-])+//g;t' <<< "http://aaa.com.tw
https://aa-a.com.tw
http://aaa.com
https://aaa.com
aaa.com
aaa.com.tw"
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