on-the-fly output redirection, seeing the file redirection output while the program is still running

Question

If I use a command like this one:
./program >> a.txt &
, and the program is a long running one then I can only see the output once the program ended. That means I ha

Answer 1

Have you considered piping to tee?

./program | tee a.txt

However, even tee won't work if "program" doesn't write anything to stdout until it is done. So, the effectiveness depends a lot on how your program behaves.