# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/.*Function=\"([^\"]*).*/\1/g;t' <<< "[1] ID=Gfo_R000001;Source=ENST00000513418;Function=\"SMAD5\";
[2] ID=Gfo_R000002;Source=ENSTGUT00000017468;Function=\"CENPA\";
[3] ID=Gfo_R000003;Source=ENSGALT00000028134;Function=\"C1QL4\";
[4] ID=Gfo_R000004;Source=ENSTGUT00000015300;Function=\"\";
[5] ID=Gfo_R000005;Source=ENSTGUT00000019268;Function=\"\";
[6] ID=Gfo_R000006;Source=ENSTGUT00000019035;Function=\"\";
"
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