DUP(2)                                                     DUP(2)



     NAME
          dup - duplicate an open file descriptor

     SYNOPSIS
          int dup (fildes)
          int fildes;

     DESCRIPTION
          Fildes is a file descriptor obtained from a creat, open,
          dup, fcntl, or pipe system call.  dup 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.

          dup will fail if one or more of the following are true:

          [EBADF]        Fildes 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                         that machine is no longer active.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.

     ORIGIN
          AT&T V.3








     Page 1                                        (last mod. 8/20/87)