# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/((?s)(\[)(\d)(\])([ ])(?=.*:LOOKUP\3=(\w+))|(\[(\d+)\])[ ])((?<artist1>Frank Sinatra)?(\s-\s)(?<title1>.*)(?<ext1>\..*)|(?<title2>.*)(\s-\s)(?<artist2>Frank Sinatra)(?<ext2>\..*)|(?<title3>.*)(?<ext3>\..*))|(?<dict>RegExDictionary:.*)$/$6$8${title1}${title2}${title3}${ext1}${ext2}${ext3}/gmi;t' <<< "[8] Frank Sinatra - One For My Friend.flac
[51] Come Fly With Me - Frank Sinatra.dsf
[2] Frank Sinatra - Love Me Tender.flac
[17] New York, New York.mp3
[45] Singing In The Rain - Frank Sinatra.flac
RegExDictionary:LOOKUP0=00:LOOKUP1=01:LOOKUP2=02:LOOKUP3=03:LOOKUP4=04:LOOKUP5=05:LOOKUP6=06:LOOKUP7=07:LOOKUP8=08:LOOKUP9=09"
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