1: int save_out = dup(fileno(stdout));//backup stdout

2: int out = open("cout.log", O_RDWR|O_CREAT|O_APPEND, 0600);

3: int  nRet;

4: fflush(stdout);

5: dup2(out, fileno(stdout));// redirect stdout to out

8: printf("Hello world!");

10: fflush(stdout);close(out);close(stdout);

11: dup2(save_out, fileno(stdout));//return the backup

12: close(save_out);

 

include the header file #include <fcntl.h>