Make output line-buffered by default (#894)
Make output line-buffered by default (#894)

This is a pretty typical use case:

    bpftrace -e 'kprobe:some_function { printf("hello world\n"); }'

If `some_function` is not hit very often, or just once during your
tracing session, `hello world` may not show up until you exit bpftrace.
This can lead to confusing experiences.

This patch makes the output line buffered by default. It also preserves
the `-B line` flag for compatibility but removes it from the help text.
iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace