Using fgets(char* c, int i, file* f) with printf() for C in Eclipse - CDT. The order of output is not correct.!

Question

#include <stdio.h>
enum { max_string = 127 };
static char ch[max_string+1] = "";

int main(int argc, char ** argv){
    printf("Type a String: \n");
    fgets(ch, max_string, stdin);
    printf("the string is: %s", ch);
    return 0;
}

I have used this code and the output in the console was

hello world
Type a String: 
the string is: hello world

'hello world' is the input which I give.

My question is why isn't the order not maintained in this case. As printf() should work before fgets(), but here it isn't that way. I have checked with the same compiler in Code::Blocks. There it works in order. But in case of Eclipse-MARS CDT I find it erroneous.

Answer 1

I assume you're running on Windows, and running into a longstanding problem with console output in Eclipse CDT on Windows.

The bug is marked as "WONTFIX", and the comments explain why it's a hard problem to fix. They do suggest several workarounds:

• Call fflush(stdout) after each call to printf. This flushes the output buffer explicitly after each output operation.
• Call setvbuf(stdout, NULL, _IONBF, 0) once at the beginning of your program. This disables output buffering altogether.
• Use CDT's experimental "winpty" support as described here. This attempts to make Eclipse's console have the same behaviour as a real terminal, including line buffering.

I have a much simpler solution to suggest: build your program with Eclipse, but run it directly from a terminal (Command Prompt). Then you will get proper terminal behaviour without any workarounds.