This separate patch to simplify the print_kth() function by removing the comparison from it, is simple and has a significant perf advantage. Tests pass so I'll apply.
I'll adjust the commit log to summarise the perf change, but I notice the change isn't as great as yours on my sandybridge i3 system. Benchmark results for both the rebased memory rework and the simple print_kth() optimization attached. thanks! Pádraig.
### small ranges $ yes abcdfeg | head -n1MB > big-file $ for c in orig split mem; do src/cut-$c 2>/dev/null; time src/cut-$c -b1,3 big-file > /dev/null; done real 0m0.083s user 0m0.080s sys 0m0.003s real 0m0.069s user 0m0.061s sys 0m0.007s real 0m0.068s user 0m0.066s sys 0m0.001s ### bigger ranges $ yes $(yes a | head -n100000 | tr -d '\n') | head -n10000 > big-lines $ for c in orig split mem; do src/cut-$c 2>/dev/null; time src/cut-$c -b50-100,101-105,9999 big-lines > /dev/null; done real 0m9.951s user 0m9.065s sys 0m0.810s real 0m8.542s user 0m7.586s sys 0m0.876s real 0m10.149s user 0m8.875s sys 0m1.145s ### fields yes "a:b:c:d:e" | head -n1MB > fields $ for c in orig split mem; do src/cut-$c 2>/dev/null; time src/cut-$c -f2,3 -d: fields > /dev/null; done real 0m0.172s user 0m0.167s sys 0m0.004s real 0m0.149s user 0m0.146s sys 0m0.003s real 0m0.145s user 0m0.141s sys 0m0.004s ### --output-delimiter $ for c in orig split mem; do src/cut-$c 2>/dev/null; time src/cut-$c -f2,3 -d: --output-d=' ' fields > /dev/null; done real 0m0.159s user 0m0.153s sys 0m0.005s real 0m0.144s user 0m0.141s sys 0m0.003s real 0m0.137s user 0m0.133s sys 0m0.004s
