Accessing Files Programmer's Guide (32650-90885)

84 Chapter3
Specifying a File Designation
Parsing and Validating File Designators
Parsing and Validating File Designators
The FPARSE intrinsic parses and validates a file designator string to determine if it is
syntactically correct. You can employ this intrinsic to check a formal file designator
representing a file before attempting to open the file with HPFOPEN/FOPEN. MPE/iX file
designators used for the file system and two user interface commands include a remote
environment ID (
envid ). This allows the user to indicate that a file is to be accessed from a
remote environment established by the user with the DSLINE or REMOTE HELLO command.
FPARSE facilitates the changes required for the file designator extension. It provides the
only location within MPE/iX where file designators are parsed and syntax is checked.
The following are examples of the
items and the vectors array pair. The order of entries
in the
vectors array corresponds to the order of items in the items array. Each 32-bit
entry in the
vectors array returns the byte offset of the item in the first half-word, and
the length in bytes of the item in the second half-word. However, the last entry of the
vectors array has a different meaning from that of the other entries: the second half-word
gives the total length of the file string, and the first half-word gives a system file code when
applicable.
In Figure 3-3. the file string is
"FILENAME/LOCKWORD.GROUP.ACCOUNT:ANIMAL.INDDCL.HPBCG":
Figure 3-3. Illustration of FPARSE Usage
The
items array, as illustrated above, can be listed in any order or can be left unspecified if
not required.
In Figure 3-4., below, the file string is "*FILENAME:ANIMAL":