DUP(2-SVR3)         RISC/os Reference Manual          DUP(2-SVR3)



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.

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

     [EBADF]             fildes is not a valid open file descrip-
                         tor.

     [EINTR]             A signal was caught during the dup sys-
                         tem 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                         link to that machine is no longer
                         active.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.







                        Printed 11/19/92                   Page 1