unbuffer connects to a command via a pseudo-terminal (pty), which makes the system treat it as an interactive process, therefore not using any stdout buffering.

What is the equivalent of unbuffer program on Windows?

unbuffer is actually just an expect script that comes with expect

When you have a pipeline, unbuffer must be applied to each element except the last (since that doesn't have its output redirected). Example: unbuffer p1 | unbuffer p2 | unbuffer p3 | p4

unbuffer disables the output buffering that occurs when program output is redirected. For example, suppose you are watching the output from a fifo by running it through od and then more.    od -c /tmp/fifo | more You will not see anything until a full page of output has been produced. You can disable this automatic buffering as follows:    unbuffer od -c /tmp/fifo | more