Why does tee wait the end of the .exe program?

Question

I am on a Windows 7 host with cygwin 1.7.0 installed.

I want to see the output of myTest.exe on the console and in the meanwhile have it written to myTest.log, but all output is shown only when myTest.exe is concluded.

I tried the solution suggested here and this works good. Then I wrote the following myTest.c:

#include <stdio.h>
#include <Windows.h>

int main() {
    printf ("hello\n");
    Sleep(5000);
    printf("goodbye\n");
    return 0;
}

and compile it with the command

gcc myTest.c -o myTest

Executing test.exe without tee works as expected, but if I execute

./myTest.exe | tee myTest.log

I get all output on the console only after myTest.exe is done.

Any suggestions how I can get the output to the console while myTest.exe is still running?

Answer 1

The console output is buffered, so when the program exits, it flushes the buffer. You'll need to explicitly flush the buffer before the sleep so that it gets written immediately. For example:

fflush(stdout);