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 and DragonFly
5.5.