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



NAME
     dup, dup2 - duplicate an open file descriptor

SYNOPSIS
     int dup(fildes)
     int fildes;

     int dup2(fildes, fildes2)
     int fildes, fildes2;

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

     dup returns a new file descriptor which refers to the same
     open file description as fildes, and shares any locks.  The
     file descriptor returned is the lowest one available.

     dup2 forces fildes2 to access the same open file description
     as fildes.  If fildes2 already references an open file
     description, the file associated with fildes2 is closed,
     unless fildes2 equals fildes.  If fildes is not a valid file
     descriptor, dup2 fails and does not close fildes2.

     The new file descriptor returned by dup and dup2 is set to
     remain open across exec system calls [see fcntl(2)].

ERRORS
     dup and dup2 will fail if one or more of the following are
     true:

     [EBADF]             fildes or fildes2 is not a valid open
                         file descriptor, or fildes2 is negative
                         or greater than or equal to {OPEN_MAX}.

     [EINTR]             A signal was caught during the dup2 sys-
                         tem call.

     [EMFILE]            The number of open file descriptors
                         would exceed {OPEN_MAX}.

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

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.







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