# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/^(?:'''\n?)?((?:.*?)(?:\n.*?)*?)(?:\n?'''\n?)?$/'''\n$1\n'''/g;t' <<< "'''
MATCH THE TEXT WITH ZERO, ONE OR NO DELIMITERS:
ADD MISSING OPENING AND/OR CLOSING DELIMITER
(NOTE: ALSO MATCHES WITH BOTH DELIMITERS)
sad
fsd
f
sdasdf
dsf
'''"
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