dup(2) — sys5



DUP(2)          DOMAIN/IX Reference Manual (SYS5)          DUP(2)



NAME
     dup - duplicate an open file descriptor

USAGE
     int dup (fildes)
     int fildes;

DESCRIPTION
     Fildes is the name of a file descriptor returned by a creat,
     open, dup, fcntl, or pipe system call.  Dup returns a new
     file descriptor with the following characteristics 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 remains open across exec system
     calls.  See fcntl(2).

     The file descriptor returned is given the lowest number
     available.

RETURN VALUE
     Dup returns a non-negative integer, the file descriptor,
     upon successful completion.  Otherwise, it returns -1 and
     sets errno to specify the error.

ERRORS
     Dup fails if one or more of the following is true:

     [EBADF]        Fildes is not a valid open file descriptor.

     [EMFILE]       The maximum number of open file descriptors
                    allowed would be exceeded.

RELATED INFORMATION
     creat(2), close(2), exec(2), fcntl(2), open(2), pipe(2)














Printed 5/10/85                                             DUP-1
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