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

If you're trying to modify the behavior of an existing program try stdbuf (part of coreutils starting with version 7.5 apparently).

This buffers stdout up to a line:

stdbuf -oL command > output

This disables stdout buffering altogether:

stdbuf -o0 command > output