Linux non-blocking fifo (on demand logging)

Question

I like to log a programs output \'on demand\'. Eg. the output is logged to the terminal, but another process can hook on the current output at any time.

The classic

Answer 1

It seems like bash <> redirection operator (3.6.10 Opening File Descriptors for Reading and WritingSee) makes writing to file/fifo opened with it non-blocking. This should work:

$ mkfifo /tmp/mylog
$ exec 4<>/tmp/mylog
$ myprogram 2>&1 | tee >&4
$ cat /tmp/mylog # on demend

Solution given by gniourf_gniourf on #bash IRC channel.