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DUP3(3) Library Functions Manual DUP3(3)

dup3duplicate an existing file descriptor

library “libc”

#include <fcntl.h>
#include <unistd.h>

int
dup3(int oldd, int newd, int flags);

The () 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 olddnewd and flags == 0, the behavior is identical to dup2(oldd, newd).

If oldd == newd, then () fails, unlike dup2(2).

The value -1 is returned if an error occurs. The external variable errno indicates the cause of the error.

The dup3() function fails if:

[]
The oldd argument is not a valid active descriptor or the newd argument is negative or exceeds the maximum allowable descriptor number
[]
The oldd argument is equal to the newd argument.
[]
The flags argument has bits set other than O_CLOEXEC.

accept(2), close(2), dup2(2), fcntl(2), getdtablesize(2), open(2), pipe(2), socket(2), socketpair(2)

The dup3() function does not conform to any standard.

The dup3() function appeared in FreeBSD 10.0 and DragonFly 5.5.

August 16, 2013 DragonFly-5.6.1