UNIX for Advanced & Expert Users

Code:

int redirect()
{
 int fd,rc;
 fd = open("sample.DAT",O_CREAT | O_RDWR , 00777 );
 rc = dup2(fd , 1 ) ;
 close (fd );
return 0;
}

I used the above to redirect all the cout statements to sample.DAT. process is redirecting the output and I had two questions

1. All stdout/cout statements for that current process will be redirected to sample.DAT. correct?

2. If the file is deleted in the middle of the redirection of stdout statements and if recreated that file manually it will not redirect the output?
To do redirection even if the file deleted do I have to recall redirect method? If I recall redirect method then what will happen to the existing duplicated filedescriptor. will that result more no of opened file descriptors?

yes.

Correct.

yes, exactly.

dup2 close the newfd (here stdout) first. So you won't have descriptor leaks.

To conclude, a few remarks about your redirect:
- check whether the function open() and dup2() were successful or not.
- use the constant STDOUT_FILENO instead of 1 for dup2(). (this constant is defined in <unistd.h>)

HTH,
Loïc.

Thanks for your clarifications. Thank you and understood that before duplicating it will close the existing file descriptor "1" if any and duplicates new fd to 1.