# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(\d+)\s+([A-Z]+)(\d+)\s+(\w+)/$1+$2+$3+$4/g;t' <<< "6876786786 GFS8978976 I
6786786767 DDF78676 I
4343245443 SBSSK67676 I
8393372263 SBSSK56565 I
6545434347 DDF7878333 I
6757650000 SBSSK453 I"
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