Aint fd=open("log.txt", O_WRONLY|O_CREAT, 0644); flag=fcntl(fd, F_GETFL); flag|=O_SYNC; fcntl(fd, F_SETFL, flag);
Bint fd=open("log.txt", O_WRONLY|O_CREAT|O_SYNC, 0644);
Cint fd=open("log.txt", O_WRONLY|O_CREAT, 0644); flag=fcntl(fd, F_GETFL); flag|=O_NONBLOCK; fcntl(fd, F_SETFL, flag);
Dint fd=open("log.txt", O_WRONLY|O_CREAT, 0644); flush(fd);