ID Number: Q72744
3.00 3.10
WINDOWS
Summary:
To determine whether the SHARE.EXE application is loaded, an
application typically calls MS-DOS Interrupt 2Fh Function 1000h.
However, this method always returns true in enhanced mode Microsoft
Windows version 3.0 even if the SHARE is not loaded.
Windows returns true for Interrupt 2Fh Function 1000h to prevent SHARE
from installing itself in a MS-DOS virtual machine (VM) under Windows.
If SHARE installed a local copy in a VM, the system would become
unstable and data corruption on the hard drive(s) might result.
More Information:
To determine under enhanced mode Windows whether SHARE is installed,
call Interrupt 21h Function 5Ch to lock a region of a file. This
function is available only when SHARE is installed, and unlike using
the OpenFile function with sharing modes, the lock region function
always fails with error 1 (invalid function) if SHARE is not loaded.
Perform the following six steps to determine whether SHARE is loaded:
1. Create a temporary file using MS-DOS Interrupt 21h Function 5Ah.
2. Lock a region of the returned temporary file using MS-DOS Interrupt
21h Function 5Ch. Set AL = CX = DX = SI = 0 and DI = 1.
3. If the call in step 2 returns with the carry flag set and AX = 1,
SHARE is not loaded. Move to step 5.
4. SHARE is loaded. Unlock the region of the file using MS-DOS
Interrupt 21h Function 5Ch. Set CX = DX = SI = 0 and AL = DI = 1.
5. Close the file using MS-DOS Interrupt 21h Function 3Eh.
6. Delete the file using MS-DOS Interrupt 21h Function 41h.
Note that the drive on which the temporary file is created is
important in a network environment. Typically, SHARE is always loaded
for network drives; however, a copy of SHARE is running on the server,
not on the workstation. Therefore, the application should run the test
above against the drive(s) from which it will access files.
Additional reference words: 3.00 3.10