sed -nE '/^.{101,149}$/p' infile

grep -E '^.{101,149}$' infile

awk 'length($0)>100 && length($0)<150' infile

while read l; do nc=$(<<< "$l" wc -c); [ $nc -ge 101 ] && [ $nc -le 149 ] && echo "$l"; done < file