Interrupt 21h Function 440Dh Minor Code 6Dh

Enumerates open files on the specified drive.

mov ax, 440Dh           ; generic IOCTL
mov bx, DriveNum        ; see below
mov ch, 08h             ; device category (must be 08h)
mov cl, 6Dh             ; Enumerate Open Files 
mov dx, seg PathBuf     ; see below
mov ds, dx
mov dx, offset PathBuf
mov si, FileIndex       ; see below
mov di, EnumType        ; see below
int 21h

jc  error
mov [OpenMode], ax      ; mode file was opened in
mov [FileType], cx      ; normal file or memory-mapped file

Parameters

DriveNum: Drive on which to enumerate the files. This parameter can be 0 for the default drive, 1 for A, 2 for B, and so on.
PathBuf: Address of a buffer that receives the path of the open file. The length of the buffer varies depending on the volume. Get Volume Information (Interrupt 21h Function 71A0h) is used to determine the maximum allowed length of a path for the volume.
FileIndex: Index of the file to retrieve the path for.
EnumType: Kind of file to enumerate. This parameter can be 0 to enumerate all open files or 1 to enumerate only open unmovable files, including open memory-mapped files and other open unmovable files (32-bit Windows-based DLLs and executables).

Return Value

Clears the carry flag, copies the path of an open file to the given buffer, and sets the AX and CX registers to the following values if successful:

AX	Mode that the file was opened in, which is a combination of access mode, sharing mode, and open flags. It can be one value each from the access and sharing modes and any combination of open flags.
	Access modes
	OPEN_ACCESS_READONLY (0000h)
	OPEN_ACCESS_WRITEONLY (0001h)
	OPEN_ACCESS_READWRITE (0002h)
	OPEN_ACCESS_RO_NOMODLASTACCESS (0004h)
	Share modes
	OPEN_SHARE_COMPATIBLE (0000h)
	OPEN_SHARE_DENYREADWRITE (0010h)
	OPEN_SHARE_DENYWRITE (0020h)
	OPEN_SHARE_DENYREAD (0030h)
	OPEN_SHARE_DENYNONE (0040h)
	Open flags
	OPEN_FLAGS_NOINHERIT (0080h)
	OPEN_FLAGS_NO_BUFFERING (0100h)
	OPEN_FLAGS_NO_COMPRESS (0200h)
	OPEN_FLAGS_ALIAS_HINT (0400h)
	OPEN_FLAGS_NOCRITERR (2000h)
	OPEN_FLAGS_COMMIT (4000h)
CX	File type. It can be one of the following values:
	0	For normal files
	1	For a memory-mapped files (memory-mapped files are unmovable)
	2	For any other unmovable files (32-bit Windows-based DLLs and executables)
	4	For the swap file

Note that if a memory-mapped file is returned (CX = 1), the value returned in the AX register is limited to the following values:

OPEN_ACCESS_READONLY (0000h)

OPEN_ACCESS_READWRITE (0002h)

Otherwise, the function sets the carry flag and sets the AX register to the following error value:

ERROR_ACCESS_DENIED

The value of FileIndex exceeds the number of open files on the drive.

Remarks

This function returns information about one file at a time. To enumerate all open files, the function must be called repeatedly with FileIndex set to a new value for each call. FileIndex should be set to zero initially and then incremented by one for each subsequent call. The function returns the ERROR_NO_MORE_FILES error value when all open files on the volume have been enumerated.

This function may return inconsistent results when used to enumerate files on an active volume — that is, on a volume where other processes may be opening and closing files. Applications should use Lock Logical Volume (Interrupt 21h Function 440Dh Minor Code 4Ah) to take a level 3 lock before enumerating open files.