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Inside Macintosh: Files /
Chapter 1 - Introduction to File Management / File Management Reference
File and Directory Manipulation Routines / Opening, Creating, and Deleting Files


You can use the FSpOpenDF function to open a file's data fork.

FUNCTION FSpOpenDF (spec: FSSpec; permission: SignedByte;
                     VAR refNum: Integer): OSErr;
An FSSpec record specifying the file whose data fork is to be opened.
A constant indicating the desired file access permissions.
A reference number of an access path to the file's data fork.
The FSpOpenDF function opens the data fork of the file specified by the spec parameter and returns a file reference number in the refNum parameter. You can pass that reference number as a parameter to any of the low- or high-level file access routines.

The permission parameter specifies the kind of access permission mode you want. You can specify one of these constants:

   fsCurPerm      =  0;    {whatever permission is allowed}
   fsRdPerm       =  1;    {read permission}
   fsWrPerm       =  2;    {write permission}
   fsRdWrPerm     =  3;    {exclusive read/write permission}
   fsRdWrShPerm   =  4;    {shared read/write permission}
In most cases, you can simply set the permission parameter to fsCurPerm. Some applications request fsRdWrPerm, to ensure that they can both read from and write to a file.

noErr0No error
nsvErr-35No such volume
ioErr-36I/O error
bdNamErr-37Bad filename
tmfoErr-42Too many files open
fnfErr-43File not found
opWrErr-49File already open for writing
permErr-54Attempt to open locked file for writing
dirNFErr-120Directory not found or incomplete pathname
afpAccessDenied-5000User does not have the correct access to the file

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© Apple Computer, Inc.
2 JUL 1996