Hierarchy of File Overrides

The :FILE command cannot o verride at run time an y speci￿cations in the disc ￿le label for an existing disc ￿le. (The ￿le label speci￿es ph ysical characteristics of the ￿le; record structure, ￿le structure, ￿le code, and actual ￿le name.) An ything in the disc ￿le label has precedence. Similarly, device characteristics alwa ys prevail over a :FILE command invoked for a device ￿le. :FILE can override the following:

Speci￿cations that are not in a ￿le label for a disc ￿le.

Speci￿cations that are not already giv en for a device ￿le.

Speci￿cations giv en when an intrinsic in the program opens the ￿le.

If the program creates a disc ￿le at run time, then :FILE can override the opening characteristics that the program w as compiled to use and create a ￿le with di￿eren t characteristics.

It is possible to use an in trinsic such as HPFOPEN or FOPEN to override ￿le equations. When an intrinsic is set up to do this, the ￿le equation produced b y invoking :FILE can be ignored unless the ￿le name giv en in the intrinsic opening the ￿le is dereferenced (preceded b y an asterisk (*)). For detailed information on the hierarc hy of overrides, and for information on how this applies to labeled tapes, refer to Accessing Files Pr ogrammer's Guide (32650-90017).

When a :FILE command is entered that contradicts some of the HPFOPEN or FOPEN parameters for a ￿le, The File System main tains a hierarc hy of overrides, as sho wn in Figure 6-11 .

Figure 6-11. File System Hierarchy of Overrides

File System 6-21