Pipe netstat output multiple times

I want to store current开发者_如何学C network traffic [b/s] in Mac OS X into a file once a second.

netstat -b -n 1 |awk '{print $3}' |tail -n +3 >traffic.txt

should do want I want to - but the second pipe seems to be buffered, and I need the results as soon as possible.

If I only use one pipe, everything's fine, but I need at most these three.

ulimit -p 0 doesn't work (not implemented?). Is there any other way to avoid buffering?

awk will buffer its output by default. Call fflush() to flush it.

netstat -b -n 1 |awk '{print $3;fflush()}' |tail -n +3 >traffic.txt

Pipes are buffers, and they will send along data when they get around to it. I don't know of a way to speed them along.

Also, did you mean >> traffic.txt at the end? Your solution would truncate, two angle brackets appends.