FSpOpenDF You can use the FSpOpenDF function to open a file's data fork. A constant indicating the desired file access permissions. 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. The permission parameter specifies the kind of access permission mode you want. 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.
In shared environments, permission requests are translated into the deny mode permissions defined by AppleShare. Inc. All rights reserved.