NAME
dup3 —
duplicate an existing file
descriptor
LIBRARY
library “libc”
SYNOPSIS
#include <fcntl.h>
#include <unistd.h>
int
dup3(int
oldd, int newd,
int flags);
DESCRIPTION
Thedup3()
function duplicates an existing object descriptor while allowing the value of
the new descriptor to be specified.
The close-on-exec flag on the new file descriptor is determined by
the O_CLOEXEC bit in
flags.
If oldd ≠ newd
and flags == 0, the behavior is identical to
dup2(oldd, newd).
If oldd ==
newd, then
dup3()
fails, unlike dup2(2).
RETURN VALUES
The value -1 is returned if an error occurs. The external variable errno indicates the cause of the error.
ERRORS
The dup3() function fails if:
- [
EBADF] - The oldd argument is not a valid active descriptor or the newd argument is negative or exceeds the maximum allowable descriptor number
- [
EINVAL] - The oldd argument is equal to the newd argument.
- [
EINVAL] - The flags argument has bits set other than
O_CLOEXEC.
SEE ALSO
accept(2), close(2), dup2(2), fcntl(2), getdtablesize(2), open(2), pipe(2), socket(2), socketpair(2)
STANDARDS
The dup3() function does not conform to
any standard.
HISTORY
The dup3() function appeared in
FreeBSD 10.0.