c - Instant redirect program output to file without buffering from batch file -

i have c program messages printed printf command. batch file call program with

call myprogram.exe parms > myfile.txt 

i need myfile updated every time (or every time) when myprogram print message. now, cannot see in file until program finish execution, because buffering. buffering problem c program, batch file or operating system, , how can resolve it?

stdio.h functions buffering. see setvbuf. buffering may operating system specific, , may change when redirecting (e.g. because internally isatty(3) used inside printf etc...).

^{notice buffering useful, , speeds output lot.}

the simplest way call fflush(3) time time. otherwise call setvbuf _iofbf on stdout.

using setvbuf near start of program simpler. however, calling fflush @ appropriate places might more efficient (because using larger buffer should faster).