dup2(2)                    DG/UX 4.30                     dup2(2)



     NAME
          dup2 - Duplicate an open file descriptor onto a specific
          descriptor.

     SYNOPSIS
          int    dup2  (old_fildes, new_fildes)
          int             old_fildes;
          int             new_fildes;

     PARAMETERS
          old_fildes     A valid, active file descriptor.


          new_fildes     Another file descriptor.

     DESCRIPTION
          Dup2 combines the functionality of the dup and close
          operations.

          If <old_fildes> is an active, valid descriptor and
          <new_fildes> is a valid descriptor (active or not),
          <new_fildes> is made a duplicate of <old_fildes>.  If
          <old_fildes> and <new_fildes> already refer to the same
          object pointer, no changes occur.  In all other situations
          in which <new_fildes> is active, it is closed before being
          made a duplicate of <old_fildes>.  The close-on-exec flag is
          set so the descriptor remains open across exec(2)
          operations.  For a further discussion of the semantics of
          duplication and closing, see the dup and close operations
          respectively.

          If <old_fildes> equals <new_fildes>, no changes occur.
          However, an error will be returned if <old_fildes> is not an
          active, valid descriptor.

     ACCESS CONTROL
          None.

     RETURN VALUE
          <new_fildes>   The value of the new file descriptor given by
                         <new_fildes>.


          -1             An error occurred.  Errno is set to indicate
                         the error.

     EXCEPTIONS
          Errno may be set to one of the following error codes:


          EBADF          <Old_fildes> is not a valid, active
                         descriptor.



     Licensed material--property of copyright holder(s)         Page 1

     dup2(2)                    DG/UX 4.30                     dup2(2)



          EBADF          <New_fildes> is not a valid descriptor.

     SEE ALSO
          The related manual sections:  accept(2), close(2), creat(2),
          dup(2), exec(2), fcntl(2), getdtablesize(2), open(2),
          pipe(2), socket(2), socketpair(2).

     STANDARDS
          When using m88kbcs as the Software Development Environment
          target, the dup2 function will be emulated using BCS system
          calls. Since this is an emulation requiring several BCS
          system calls, a slight performance degradation may be
          noticed in comparison to using dup2 in /lib/libc.a.










































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