use PeekNamedPipe to check bytes available

nb_available.c

#include <windows.h>
#include <stdio.h>
#include <stdbool.h>

#define BUFSIZE 1024

int main(int ac, char** av) {
    
    HANDLE h = GetStdHandle(STD_INPUT_HANDLE);
    DWORD rd;

    CHAR chBuf[BUFSIZE];
    DWORD dwRead;
    bool bSuccess = FALSE;
    
    while(1) {

        if (!PeekNamedPipe(h, NULL, 0, NULL, &rd, NULL)) {
            printf("eof\n");
            return 1;
        }
        
        if (rd > 0) {
                
            ReadFile(h, chBuf, BUFSIZE, &dwRead, NULL);
            
            chBuf[dwRead] = '\0';
            printf("dwRead: %d\n", dwRead);
            printf("read: %s\n", chBuf);

            Sleep(1000);

        } else {
            Sleep(1000);

        }
    }
    
    return 0;

}