OpenWD

Open a new working directory

#include <Files.h> File Manager (PBxxx)

OsErr OpenWD( vRefNum, dirID, procID, wdRefNum);

short vRefNum; volume, drive or working directory dir reference

long dirID; working directory's directory ID

long procID; working dir user ref (app's signature or 0)

short *wdRefNum; newly created working directory reference number

returns Error Code; 0=no error

OpenWD creates a new working directory. It is similar to PBOpenWD, but

uses refNums and dirID's instead of a WDPBRec. A working directory number

can be used whenever a volume reference number is required.

Returns: an operating system Error Code. It will be one of:

noErr (0) No error

tmwdoErr (-121) Too many working directories open

Notes: "Working directories" exist as a way to maintain compatibility with the

flat file system of the original Macintosh. In effect, a working directory

reference number is just a 16-bit alias for a 32-bit "hard" directory ID

and a "real" volume reference. When the File Manager sees a working

directory reference in a volume reference number (e.g., ioVRefNum of any

parameter block), it looks up the real directory number and uses that value

in finding files.

Note: This notion of a working directory is very different from that of a

"current default directory", as MS-DOS and especially UNIX programmers

might assume. See SetVol for details on setting the default volume.

The Standard File Package calls PBOpenWD each time the user selects a

directory (either by opening a folder or selecting from the drop-down list).

If the user then opens a file, the resulting working directory reference

number is returned in tr. vRefNum. Thus, if you use Standard File for file

selection, you may never need OpenWD or PBOpenWD.

Note: You can eyeball a VRefNum and see what it is: large negative

numbers such as -32456 (0x8138) are used for working directories;

small negative numbers such as -1 (0xFFFF) are real volume numbers.

The system maintains a limited number of slots for tracking working

directories. It is wise to close WDs (via PBCloseWD) as soon as possible.

Referenced by (3):