Extended file names provide a wider variety of character set
options and naming conventions, similar to those available on
Windows NT. This topic describes the impact of Extended File
Specifications on the general user, and contains the following
subtopics:
o Differences in file and directory specifications between ODS-2
and ODS-5
o Manipulating extended file names
o Using extended file names in DCL command procedures
o Displaying ODS-5 file specifications in DECwindows
1 – File Specification Differences
With extended file names, there are two possible naming styles
for file specifications: traditional (ODS-2 compliant) and
extended (ODS-5 compliant). The following topics describe these
naming styles.
See also the OpenVMS User's Manual and the Guide to OpenVMS File
Applications for more information about file specifications in
Extended File Specifications.
1.1 – ODS-2 Syntax
The traditional (ODS-2) file name syntax is the syntax most
OpenVMS users have been accustomed to up to the advent of
extended file names. OpenVMS Versions 7.1 and earlier follow this
syntax, which supports the following character set and naming
conventions.
ODS-2 Character Set
The ODS-2 character set consists of alphanumeric characters (A-Z,
a-z, 0-9), dollar sign ($), underscore (_) and hyphen (-). The
hyphen (-) should not be used as the first or last character in a
file name. While it is possible to do this under some conditions,
special handling is required to access such a file once created.
Case Insensitivity
Case preservation is not supported with traditional syntax.
Commands may be entered in uppercase, lowercase, or mixed case;
however, all characters are stored in uppercase format.
Standard Delimiters
With traditional syntax, the file type is preceded by a period
(.). The file version is separated from the type by a semicolon
(;) or sometimes a period (.). (When the system displays file
specifications, it displays a semicolon in front of the file
version number.) Directories are enclosed by brackets ([]) or
angle brackets (<>). Directory levels are separated by periods
(.).
Limited File Length
Traditional file names follow the 39.39 format, supporting only a
single period (.) separating the name and type components.
1.2 – ODS-5 Syntax
The extended (ODS-5) file name syntax offered by Extended File
Specifications supports a larger character set and relaxes
restrictions on lengths of file names and use of characters. This
syntax allows Windows NT-style file names that use the following
character set and naming conventions to be stored on and accessed
by OpenVMS systems.
1.2.1 – Character Set Support
The ISO Latin-1 Multinational character set is a superset
of the traditional ASCII character set used by versions of
OpenVMS previous to 7.2. With extended file specifications, all
characters from the 8-bit ISO Latin-1 Multinational character set
are valid in file specifications, except the following:
C0 control codes (0x00 to 0x1F inclusive)
Double quotation marks (")
Asterisk (*)
Backslash (\)
Colon (:)
Left angle bracket (<)
Right angle bracket (>)
Slash (/)
Question mark (?)
Vertical bar (|)
File specifications on an ODS-5 volume can also include Unicode
(UCS-2) characters. Because each Unicode character requires
two bytes, the use of Unicode characters can affect the maximum
permitted lengths of file specifications.
1.2.2 – Special Characters
Some ISO Latin-1 characters require the circumflex (^) to precede
them in a file specification in order to be interpreted as
literal characters rather than special function characters.
The circumflex (^) is interpreted by the system as an escape
character.
o The circumflex (^) followed by underscore (_) or by a space
represents a space.
o The circumflex (^) followed by any of the following characters
means that the character is to be used as part of a file name
rather than having any special meaning that it might otherwise
have in a file specification:
. , ; [ ] % ^ &
o A user can enter a literal period (.) with or without the
circumflex (^) in a file name. The system adds the circumflex
to any periods other than those that act as delimiters for the
file type and version number. Literal periods (.) in directory
names must be preceded by the circumflex.
File names containing special characters cannot be accessed
from a VAX system.
1.2.3 – Interpretation of Period
The introduction of the period (.) as a literal character in
extended file names requires RMS to determine which periods are
file name characters and which are delimiters.
When only one period (.) is used in an extended file name, that
period is interpreted as the delimiter, as in "Venice.Venezia;1"
above. As in previous versions of OpenVMS, this behavior also
occurs if the single period is followed by a number:
$ CREATE Test.1
creates the file:
Test.1;1
When there are multiple periods (.) in a file name, the system
looks at all the characters after the last period. If those
characters are five or fewer digits, or a minus sign (-) followed
by five or fewer digits, the period is interpreted as a version
delimiter and the period previous to it is a type delimiter.
Notice that a legal version is less than or equal to 32767.
If you try to create the file "grandioso.x.33333", the "33333"
causes an illegal version error. If there is a nonnumeric
character following the last period then it is interpreted as
a type delimiter.
For example, the following command: $ CREATE Test4.3.2.1
creates the file: Test4^.3.2;1
where .2 is the file type and 1 is the file version.
1.3 – Expanded File Specification Length
On an ODS-5 volume, the file name together with the file type
can be up to 236 8-bit characters of 117 16-bit characters in
length. Unmodified programs and utilities may limit or abbreviate
complete file specifications to 255 bytes.
$ CREATE This.File.Name.Has.A.Lot.Of.Periods.DAT
$ CREATE -
_$ ThisIsAVeryLongFileName^&ItWillKeepGoingForLotsAndLotsOfCha -
_$ racters.ExceedingThe39^,39presentInPreviousVersionsOfOpenVMS
$ DIRECTORY
Directory TEST$ODS5:[TESTING]
ThisIsAVeryLongFileName^&ItWillKeepGoingForLotsAndLotsOfCharac
ters.ExceedingThe39^,39presentInPreviousVersionsOfOpenVMS;1
This^.File^.Name^.Has^.A^.Lot^.Of^.Periods.DAT;1
Total of 2 files.
1.4 – Case Preservation
Mixed-case and lowercase file names are retained in their
original form on ODS-5 volumes. However, the file system on
OpenVMS preserves the case of file names as they are first
entered. When you create more than one file with the same name
differing only in case, DCL treats the subsequent files as
versions, and converts them to the same case as the original
file.
For example, the following commands:
$ CREATE CaPri.;1
$ CREATE CAPRI
$ CREATE capri
produce the resulting files:
CaPri.;1 CaPri.;2 CaPri.;3
1.5 – Using Wildcards
Single- and multiple-character wildcards still function as
expected with ODS-5 files. A single-character wildcard represents
exactly one character in either the file name or file type, but
may not be used in the file version string. A multiple-character
wildcard can represent any number of characters starting with
zero in the file name or file type. A multiple-character wildcard
can be used in place of a version string.
1.5.1 – Wildcard Characters
The following characters are wildcard characters when working on
any OpenVMS 7.2 or later volume:
o The asterisk (*) is a multiple-character wildcard.
o The percent sign (%) is a single-character wildcard.
o The question mark (?) is a single-character wildcard.
The percent sign (%) continues to be a single-character wildcard
to maintain compatibility with existing applications. The percent
sign (%) may be used as a literal character when preceded by
the circumflex (^) and is also a literal character in Windows NT
file names. Therefore, in addition to the percent sign, RMS also
recognizes the question mark (?) as a single character wildcard.
The question mark functions identically to the percent sign as
a wildcard character on OpenVMS 7.2 and later. The percent sign
and the question mark matches exactly one character in a search
pattern.
1.5.2 – Wildcard Syntax
Although DCL preserves the case of extended file names, wildcard
matching is case blind.
When you perform a search operation with wildcards it continues
to match only against the corresponding character in the same
part of the target specification. The following table contains
examples of some wildcard searches.
The
pattern... matches... ...but doesn't match
A*B;* AHAB.;1 A.B;1
A.*.B* A^.DISK.BLOCK;1 A^.C^.B.DAT;1
A?B.TXT;* A^.B.TXT;5 A^.^.B.TXT;1
*.DAT Lots^.of^.Periods.dat;1DAT.;1
Mil?no.dat Milano.dat;1 Millaano.dat;1
NAPOLI.?.DAT napoli.q.dat;1 napoli.abc77.dat;1
1.6 – Case Sensitivity and Blindness
In prior versions of OpenVMS, DCL and RMS converted all
file specifications to uppercase. When using Extended File
Specifications, the case of all file names is preserved as
created by the user.
Files and directories can have mixed case names in extended file
names.
Original
file name ODS-2 Volume ODS-5 Volume
MILANO;1 MILANO.;1 MILANO.;1
SanRemo SANREMO.;1 SanRemo.;1
genoa..1 GENOA.;1 genoa.;1
2 – Directory Specification Differences
The following topics describe the deeper directory structures and
extended naming syntax available with Extended File Specifications.
It is now possible to go beyond the eight levels of directories
previously supported in OpenVMS.
See also the OpenVMS User's Manual and the Guide to OpenVMS File
Applications for more information about directory specifications
in Extended File Specifications.
2.1 – Deep Directory Structures
OpenVMS 7.2 and later supports deep nesting of up to 255
directories with the restriction that the total directory
specification must be no longer than 512 8-bit or 16-bit
characters.
For example, a user can create the following directories on an
ODS-2 or ODS-5 volume:
$ CREATE/DIRECTORY [a.b.c.d.e.f.g.h.i.j.k.l.m]
A user can create the following directory with a long name on an
ODS-5 volume:
$ CREATE/DIRECTORY -
[.AVeryLongDirectoryNameWhichHasNothingToDoWithAnythingInParticular]
2.2 – Directory Naming Syntax
When using Extended File Specifications, directory names conform
to most of the same conventions as file names when using the
ISO Latin-1 character set. Periods and special characters may
be present in the directory name, but they must be preceded by a
circumflex (^) in order to be recognized as literal characters,
as shown in the following table:
CREATE/DIRECTORY. . . Result
[Hi^&Bye] Hi^&Bye.DIR;1
[Lots^.Of^.Periods^.In^.ThisLots^.Of^.Periods^.In^.This^
.Name.DIR;1
2.3 – Directory ID and File ID Abbreviation
Under some circumstances, a full file specification may contain
more characters than the 255 bytes allowed by unmodified
applications. If a file specification that such an application
needs exceeds 255 bytes in length, RMS generates a shorter
file specification by abbreviating the directory to a DID
abbreviation, and if necessary, the filename to a FID
abbreviation.
When the file specification is too long, RMS first attempts to
generate a shorter directory specification by identifying the
directory with its directory ID. This shorter specification is
referred to as a DID abbreviation.
TEST$ODS5:[5953,9,0]Alghero.TXT;1
Note that this form of the directory name must have three numbers
and two commas to avoid ambiguity with UIC format directory
names. With the DIRECTORY command you can view the shorter
DID abbreviation version as well as the full version of a file
specification.
3 – Working in Mixed Environments
If working in an environment which contains both OpenVMS Alpha
and OpenVMS VAX systems, it becomes more important to know on
which type of volume files are being created and on which type of
volume your default directory resides.
When accessing an ODS-5 volume, you need to set the parse style
to EXTENDED to accept and display extended file specifications.
The default setting is TRADITIONAL. To set the parse style, enter
the command:
$ SET PROCESS/PARSE_STYLE=EXTENDED
When working in a mixed environment of OpenVMS VAX and OpenVMS
Alpha, it is important for users to realize upon which system
they are working. OpenVMS 7.2 and later allows VAX systems to
mount ODS-5 volumes; however users on OpenVMS VAX systems can
access only files with ODS-2-compliant file names.
When working in a mixed environment of ODS-2 and ODS-5 volumes,
keep in mind the restrictions of ODS-2 file names when creating
files on ODS-5 volumes. If a file is created with special
characters on an ODS-5 volume, the file must be given an ODS-2
compliant name if it is copied to an ODS-2 volume.
4 – DCL Command Parameters
Command procedures that use file names as parameters can produce
different results in an ODS-5 environment.
You can switch from the TRADITIONAL to the EXTENDED parse style,
and this section describes the following areas that may be
affected if you choose to do so:
o Command procedure file specification
o Case preservation and $FILE
o Ampersand versus apostrophe substitution
5 – Command File Specification
If indirect command procedures are used, you may need to put
quotes around file specifications.
The following examples show the differences in output between
TRADITIONAL and EXTENDED parse styles when using the same command
file, SS.COM:
$ create ss.com
$ if p1 .nes. "" then write sys$output "p1 = ",p1
$ if p2 .nes. "" then write sys$output "p2 = ",p2
$ if p3 .nes. "" then write sys$output "p3 = ",p3
o Setting the parse style to an ODS-2 environment and running
SS.COM, the following output occurs:
$ set process/parse_style=traditional
$ @ss ^ p2 p3
p1 = ^
p2 = P2
p3 = P3
Note that the circumflex (^) is the first argument, and that
the case is not preserved for the p2 and p3 variables.
o Setting the parse style to an ODS-5 environment, the following
output occurs when running the same command procedure:
$ set process/parse_style=extended
$ @ss ^ p2 p3
p1 = ^ P2
p2 = P3
Note that the command procedure recognizes the circumflex (^)
as the escape character, and "^ P2" is the first argument.
o Adding quotes to the circumflex (^) produces the following
outcome:
$ @ss "^" p2 p3
p1 = ^
p2 = P2
p3 = P3
Because the circumflex (^) is within a quoted string, it is
not treated as an escape character.
o Adding quotes to the p3 variable produces the following
outcome:
$ @ss "^" p2 "p3"
p1 = ^
p2 = P2
p3 = p3
Note that the case is preserved for the p3 variable.
o In an ODS-2 environment, the following command treats the
circumflex (^) and the p2 and p3 strings as arguments, and the
command procedure produces the following results:
$ set process/parse_style=traditional
$ @ss^ p2 p3
p1 = ^
p2 = P2
p3 = P3
o In an ODS-5 environment, the circumflex (^) is treated as
the escape character and DCL looks for the file "SS^_P2.COM",
which results in the following error:
$ set process/parse_style=extended
$ @ss^ p2 p3
%DCL-E-OPENIN, error opening USER$DISK:[TEST]SS^_P2.COM; as input
-RMS-E-ACC, ACP file access failed
-SYSTEM-W-BADFILENAME, bad file name syntax
5.1 – Case Preservation and $FILE
DCL attempts to preserve the casing of file specifications. It
can do this only for commands defined with the Command Definition
Utility (CDU). DCL preserves case for any item defined in the
command definition file (.CLD) with the $FILE parse type.
Refer to the Command Definition Utility manual for more
information.
5.2 – Ampersand Versus Apostrophe Substitution
You can use ampersand (&) substitution as opposed to apostrophe
substitution, to preserve case during traditional parsing.
The following traditional parsing example shows a series of
commands that change the case of a character string:
$ set process/parse_style=traditional
$ x = "string"
$ define y 'x'
$ sho log y
"Y" = "STRING" (LNM$PROCESS_TABLE)
$ define y &x
%DCL-I-SUPERSEDE, previous value of Y has been superseded
$ sho log y
"Y" = "string" (LNM$PROCESS_TABLE)
Note that the use of the ampersand (&) preserved the case of the
character string assigned to the x variable.
Apostrophe substitution takes place before the command line is
set to uppercase, and ampersand substitution takes place after
the command line is set to uppercase.
The following extended parsing example shows the same series of
commands:
$ set process/parse_style=extended
$ define y 'x'
%DCL-I-SUPERSEDE, previous value of Y has been superseded
$ sho log y
"Y" = "string" (LNM$PROCESS_TABLE)
$ define y &x
%DCL-I-SUPERSEDE, previous value of Y has been superseded
$ sho log y
"Y" = "string" (LNM$PROCESS_TABLE)
Note that both character strings for the y variable are returned
lowercase. This happens because the DEFINE command uses $FILE,
which preserves the case.
Ampersand substitution can therefore be used to specify EXTENDED
file names even though the parse style is set to TRADITIONAL, as
shown in the following example:
$ set process/parse=extended
$ cre file^ name.doc
Contents of an ODS5 file
Exit
$ set process/parse=traditional
$ a = "file^ name.doc"
$ type file^ name.doc
%DCL-W-PARMDEL, invalid parameter delimiter - check use of special
characters
\^NAME\
$ type 'a'
%DCL-W-PARMDEL, invalid parameter delimiter - check use of special
characters
\^NAME\
$ type &a
Contents of an ODS5 file
NOTE
Ampersand substitution does not work for foreign commands.
6 – DECwindows Output
When using a DECwindows DECterm terminal emulator, you must
select UPSS ISO Latin-1 from the General... submenu on the
Options menu to display the full ISO Latin-1 character set
correctly.
F$EDIT assumes that the setting is 8-Bit Multinational
Characters, as do many text editors. This can affect the output
of ODS-5-compliant file specifications.