% time cut -d, -f"1-15" numbers.csv > out.csv
0.80s user 0.11s system 100% cpu 0.906 total
% wc out.csv
  500000   500000 29174488 out.csv
% head -1 out.csv
169,970,983,721,411,426,262,255,484,174,389,651,175,975,763
% tail -1 out.csv
936,347,232,520,436,359,208,737,788,226,731,497,755,746,812