On 10/24/2012 10:12 AM, Uros Bizjak wrote:
Is it OK to call dup on the same FD the second time?
To answer my own question:
dup(4) = 9
...
close(9) = 0
dup(4) = -1 EBADF (Bad file descriptor)
Test is calling dup on a closed file descriptor. FD 4 and 9 share file
status flags.
I suspect that this is something else because this works:
open("/dev/null", O_RDONLY) = 3
dup(3) = 4
close(4) = 0
dup(3) = 4
#include <fcntl.h>
#include <unistd.h>
int
main(void)
{
int fd1 = open("/dev/null", O_RDONLY);
if (fd1 < 0) {
perror("open");
return 1;
}
int fd2 = dup(fd1);
if (fd2 < 0) {
perror("dup");
return 1;
}
if (close(fd2) < 0) {
perror("close");
return 1;
}
int fd3 = dup(fd1);
if (fd3 < 0) {
perror("dup");
return 1;
}
return 0;
}
--
Florian Weimer / Red Hat Product Security Team
