Why does my output only print if there is another print after it?

Question

Interesting little bug here:

if (host != NULL) {
    printf("hi");
} else {
    printf("FAIL");
}
return 0;

doesn't print anything at all, but:

if (host != NULL) {
    printf("hi");
} else {
    printf("FAIL");
}   
fprintf(stdout, "\n%s\n", (char *)&additionalargs);
return 0;

prints

hi

abc

Does anyone know why this is?

Answer 1

The difference is the \n characters.

As you printf characters, they are accumulated in a buffer which isn't sent to the output device until an 'end of line' character is sent.

Answer 2

printf output to stdout is buffered. You might want to look at fflush

Answer 3

try using fflush(stdout) before your if condition.