dup2(3N)                                                 dup2(3N)



     NAME
          dup2 - duplicate a descriptor

     SYNOPSIS
          dup2(oldd, newd)
          int oldd, newd;

     DESCRIPTION
          dup2 causes newd to become a duplicate of oldd.  If newd is
          already in use, the descriptor is first deallocated as if a
          close(2) call had been done first.

          The object referenced by the descriptor does not distinguish
          between references using oldd and newd in any way.  Thus if
          newd and oldd are duplicate references to an open file,
          read(2), write(3), and lseek(2) calls all move a single
          pointer into the file.  If a separate pointer into the file
          is desired, a different object reference to the file must be
          obtained by issuing an additional open(2) call.

     RETURN VALUE
          The value -1 is returned if an error occurs in either call.
          The external variable errno indicates the cause of the
          error.

     ERRORS
          dup2 fails if:

          [EBADF]
               oldd or newd is not a valid active descriptor

          [EMFILE]
               Too many descriptors are active.

     SEE ALSO
          accept(2N), open(2), close(2), pipe(2), socket(2N),
          getdtablesize(3N).


















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