HP 3000 Manuals HP 3000 Manuals
HPFDUPLICATE
NM callable only.
Creates duplicate file descriptors for files opened for MULTI, SHARED, or
EXCLUSIVE access.
Syntax
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| |
| I16 I32 I32V * |
| filenum:=HPFDUPLICATE(source,status,target);|
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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.
Related Information
Intrinsics FOPEN, HPFOPEN
Commands None
Manuals None