How to log STDOUT of a background process w/o buffering on Mac?

I am running a background process on Mac and have a problem with log update. If I run

someprog > mylog &

then mylog is updated not immediately, bu开发者_JAVA百科t with some intervals - I guess it's due to buffering. Same thing with at now. If I kill the program before output is written to mylog, then I loose the data. There was no such problem with the same program on Linux machines, so I hope I can make it run-time-updated on Mac as well. Any idea how?

someprog is a F77 program, which was not written by me.

I tried to ask this question at SuperUser, but no one can help me there.

EDIT1: I don't feel like changing the source, but keep it in mind. Logging works fine on Linux machines, so it should work on Macs as well. It must be a system setting, e.g. buffer size? It would be fine for me to limit the buffer size to a smaller value - now I have to wait hours to see something in the log.

If you have access to the source code, you can probably just add calls to fflush(stdout) after every printf. If you don't, you could try something tricky with LD_PRELOAD... Basically, make your own version of printf() that calls libc's printf... AND does a flush... Then LD_PRELOAD that library when you run... The app will use yours instead... Kinda risky tho...

That's the usual behaviour of POSIX C programs that are writing to a non-tty stream - I guess F77 shares the same behaviour, or is written in terms of the stdio routines.

I don't know what the right answer is - I guess you'll need to pipe the output through something that pretends to be a tty, but offhand I don't know what (if any) utility provides that option.