HP OpenVMS Systems Documentation
OpenVMS I/O User's Reference Manual
1.3.5 Read/Write Attributes
The read and write attributes subfunctions are used for operations suchas reading and writing file protection and creating and revising dates.A read or write attributes operation is invoked by specifying anattribute list with the QIO parameter P5. A read attributes operationcan be invoked by the major I/O function IO$_ACCESS (see Section 1.6.2);a write attributes operation can be invoked by the major I/O functionsIO$_CREATE, IO$_DEACCESS, and IO$_MODIFY (see Sections 1.6.1,1.6.3, and 1.6.4).
The read or write attributes subfunction is controlled by theattribute list specified by P5. The list consists of a variable numberof two longword control blocks, terminated by a 0 longword, as shown inFigure 1-6. The maximum number of attribute control blocks in onelist is 30. Table 1-6 describes the attribute control block fields.
Figure 1-6 Attribute Control Block Format
Table 1-7 lists the valid attributes for ACP-QIO functions. Themaximum size (in bytes) is determined by the required attributeconfiguration. For example, the Radix-50 file name (ATR$S_FILNAM) usesonly 6 bytes, but it is always accompanied by the file type and fileversion, so a total of 10 bytes is required. Each attribute has twonames: one for the code (for example, ATR$C_UCHAR) and one for the size(for example, ATR$S_UCHAR).
1Not supported for Files-11 C/D.
2Protected (can be written to only by system or owner).
3Not supported on write operations to MTAACP; defaults arereturned on read operations.
4Locked (cannot be written to while the file is locked).
5For Files-11 C/D, returns 0.
6Attributes with an ATR$C_ prefix have two names: one withthe ATR$C_ prefix for the code and one with an ATR$S_ prefix for thesize, which is not included in the list.
7Exclusive access required. This operation does not completesuccessfully if other readers or writers are allowed.
8Can be written only by the system, owner, or someoneholding READALL privilege.
9The actual length available can decrease if the file isextended in a noncontiguous manner or if an ACL is applied to the file.
10Not supported for Files-11 On-Disk Structure Level 1 ormagnetic tapes.
11The status from this attribute operation is returned inFIB$L_ACL_STATUS.
Table 1-8 lists the bits contained in the file characteristicslongword, which is read with the ATR$C_UCHAR attribute.
1Files-11 C/D only.
1.4 ACP-QIO Record Attributes Area
Figure 1-7 shows the format of the record attributes area.
Figure 1-7 ACP-QIO Record Attributes Area
Table 1-9 lists the record attributes values and their meanings.
1Defined but not implemented.
2Inverted format field. The high- and low-order 16 bits aretransposed for compatibility with PDP-11 software.
3When the end-of-file position corresponds to a blockboundary, by convention FAT$L_EFBLK contains the end-of-file VBN plus1, and FAT$W_FFBYTE contains 0.
4Variable-length record format (FAT$C_VARIABLE) only.