Linux redirect the stdout to a file

int save_out = dup(fileno(stdout));//backup stdout
int out = open("cout.log", O_RDWR|O_CREAT|O_APPEND, 0600);
int  nRet;
fflush(stdout);
dup2(out, fileno(stdout));// redirect stdout to out
printf("Hello world!");
fflush(stdout);close(out);close(stdout);
dup2(save_out, fileno(stdout));//return the backup
close(save_out);

include the header file #include <fcntl.h>