Legacy Document

Inside Macintosh: Files /

Chapter 1 - Introduction to File Management / File Management Reference

File and Directory Manipulation Routines / Opening, Creating, and Deleting Files

FSpOpenDF

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

FUNCTION FSpOpenDF (spec: FSSpec; permission: SignedByte;
                     VAR refNum: Integer): OSErr;

spec

An FSSpec record specifying the file whose data fork is to be opened.

permission

A constant indicating the desired file access permissions.

refNum

A reference number of an access path to the file's data fork.

DESCRIPTION

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:

CONST
   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.

RESULT CODES

noErr	0	No error
nsvErr	-35	No such volume
ioErr	-36	I/O error
bdNamErr	-37	Bad filename
tmfoErr	-42	Too many files open
fnfErr	-43	File not found
opWrErr	-49	File already open for writing
permErr	-54	Attempt to open locked file for writing
dirNFErr	-120	Directory not found or incomplete pathname
afpAccessDenied	-5000	User does not have the correct access to the file