MPE/iX Intrinsics Reference Manual (32650-90905)

Chapter 7 359
Command Definitions (HP32208-HPLOACNMPROC)
HPFDUPLICATE
HPFDUPLICATE
NM callable only.
Creates duplicate file descriptors for files opened for MULTI, SHARED, or EXCLUSIVE
access.
Syntax
I16 I32 I32V *
filenum :=HPFDUPLICATE( source , status , target );
Functional Return
filenum 16-bit signed integer (assigned functional return)
Returns the actual file number used to duplicate the
source file. This file
number can be different than the file number requested in the
target
parameter. If an error occurs during the duplication process, a -1 value is
returned.
Parameters
source 32-bit signed integer by value (required)
Specifies the file number to be duplicated. The file number must be a valid,
open file.
status 32-bit signed integer by reference (optional)
Returns the status of the HPFDUPLICATE call. If an error occurs and this
parameter was not specified, the functional return can be used to
determine the success or failure of the call.
target 32-bit signed integer by reference (optional)
Specifies the file number to be duplicated in the
source parameter. If the
file number is already opened, the next highest available file number is
used. The value passed must be within the legal range of file numbers. The
default value for this parameter is zero (0).
Operation Notes
When a file descriptor is duplicated, the duplicate file descriptor shares the same data
pointer as the original file descriptor in the same way that file descriptors share the same
data pointer with MULTI access. This gives you the ability to perform operations on files
that have not been previously available. Specifically, files that are opened for SHARED or
EXCLUSIVE access can now have their data pointers shared among multiple file
descriptors, at the discretion of the application that originally opens the file descriptor.