# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/^([a-z]+-[a-z]+[0-9]+-[a-z]+)$|^([a-z]+[0-9]+-[a-z]+[0-9]+-[a-z])$|^([a-z]+-[a-z]+-[a-z])$/\1\2\3/gmi;t' <<< "aaa-b3-c
a3-b6-c
aaaa-bb-c
aaa-b3-c3
a3-1b6-c
aaaa-bb-c7"
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