# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(BEGIN:VEVENT\n|(?!^)\G)(?:([A-Z;-]+)[:=][^\n]+)//g;t' <<< "BEGIN:VEVENT
SUMMARY:Marché légumes Dilbeek et bibliothèque#DTSTART;TZID=Europe/Paris:20130928T084500
DTEND;TZID=Europe/Paris:20130928T094500
DTSTAMP:20160126T214559Z
UID:aHR0cHM6Ly8xOTIuMTY4LjEuMjIwOjQ0MzIvb3duY2xvdWQvcmVtb3RlLnBocC9jYWxkYXYvY2FsZW5kYXJzL2FuZ2Vsby9kZWZhdWx0Y2FsZW5kYXIvOTkwM2QyNTctZjY2Ny00ZWI3LWFjZDEtNWJlZmI0NGQ0MmJlLmljcw==@google.com
RECURRENCE-ID;TZID=Europe/Paris:20130928T090000
SEQUENCE:1
CREATED:20160126T214559Z
LAST-MODIFIED:20160126T214559Z
STATUS:CONFIRMED
TRANSP:OPAQUE
END:VEVENT"
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