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DUP3(3) FreeBSD Library Functions Manual DUP3(3)
NAME
dup3 - duplicate an existing file descriptor
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <fcntl.h>
#include <unistd.h>
int
dup3(int oldd, int newd, int flags);
DESCRIPTION
The dup3() 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.
FreeBSD 14.0-RELEASE-p6 August 16, 2013 FreeBSD 14.0-RELEASE-p6