DUP(2)               INTERACTIVE UNIX System               DUP(2)



          NAME
               dup - duplicate an open file descriptor

          SYNOPSIS
               int dup (fildes)
               int fildes;

          DESCRIPTION
               The fildes argument is a file descriptor obtained from a
               creat, open, dup, fcntl, or pipe system call.  The dup sys-
               tem call returns a new file descriptor having the following
               in common with the original:

                    Same open file (or pipe)

                    Same file pointer (i.e., both file descriptors share
                    one file pointer)

                    Same access mode (read, write, or read/write)

               The new file descriptor is set to remain open across exec
               system calls [see fcntl(2)].

               The file descriptor returned is the lowest one available.

               The dup system call will fail if one or more of the follow-
               ing is true:

               [EBADF]        The fildes argument is not a valid open file
                              descriptor.

               [EINTR]        A signal was caught during the dup system
                              call.

               [EMFILE]       NOFILES file descriptors are currently open.

               [ENOLINK]      Fildes is on a remote machine and the link to
                              that machine is no longer active.

          SEE ALSO
               close(2), creat(2), exec(2), fcntl(2), open(2), pipe(2),
               lockf(3C).

          DIAGNOSTICS
               Upon successful completion a non-negative integer, namely
               the file descriptor, is returned.  Otherwise, a value of -1
               is returned, and errno is set to indicate the error.








          Rev. C Software Development Set                            Page 1