To append ellipsis to long lines with awk one can

echo 'blablabla' | \
  awk '{if (length($0) <= 100) print $0; else print substr($0, 1, 100) " ..."}'

.. or even

echo 'blablabla' | \
  awk '{if (length($0) <= 100) print $0; else print substr($0, 1, 100) " \033[90m...\033[0m"}'