Benchmarking yes

yes is a utility printing the provided string and a newline continuously. The default value y is used to skip the common y/n prompts provided by scripts.

Understanding yes

The most simple way to implement yes is the println! loop. But it is slow since it calls many write syscalls. So yes should print an extended string to few bytes in the loop for better throughput.

It is difficult to use hyperfine for benchmarking yes as it has infinite loop. But you can see throughput of yes by pv instead:

yes | pv >/dev/null

tee() zero-copy

The read() and write() based yes implementation is much slower than RAM's bandwidth since those syscalls are copying content of RAM.

On Linux, tee() and splice() for non-pipe output is used to avoid copying content of RAM.