The LBR$OUTPUT_HELP routine outputs help text to a user-supplied
output routine. The text is obtained from an explicitly named
help library or, optionally, from user-specified default help
libraries. An optional prompting mode is available that enables
LBR$OUTPUT_HELP to interact with you and continue to provide help
information after the initial help request has been satisfied.
Format
LBR$OUTPUT_HELP output_routine [,output_width] [,line_desc]
[,library_name] [,flags] [,input_routine]
1 – Returns
OpenVMS usage:cond_value
type: longword (unsigned)
access: write only
mechanism: by value
Longword condition value. Most utility routines return a
condition value in R0. Condition values that this routine can
return are listed under Condition Values Returned.
2 – Arguments
output_routine
OpenVMS usage:procedure
type: procedure value
access: write only
mechanism: by reference
Name of a routine that writes help text a line at a time. The
output_routine argument is the address of the procedure value
of the routine to call. You should specify either the address of
LIB$PUT_OUTPUT or a routine of your own that has the same calling
format as LIB$PUT_OUTPUT.
output_width
OpenVMS usage:longword_signed
type: longword (signed)
access: read only
mechanism: by reference
Width of the help-text line to be passed to the user-supplied
output routine. The output_width argument is the address of a
longword containing the width of the text line to be passed to
the user-supplied output routine. If you omit output_width or
specify it as 0, the default output width is 80 characters per
line.
line_desc
OpenVMS usage:char_string
type: character string
access: read only
mechanism: by descriptor
Contents of the help request line. The line_desc argument is the
address of a string descriptor pointing to a character string
containing one or more help keys defining the help requested, for
example, the HELP command line minus the HELP command and HELP
command qualifiers. The default is a string descriptor for an
empty string.
library_name
OpenVMS usage:char_string
type: character string
access: read only
mechanism: by descriptor
Name of the main library. The library_name argument is the
address of a string descriptor pointing to the main library
file specification string. The default is a null string, which
means you should use the default help libraries. If you omit the
device and directory specifications, the default is SYS$HELP. The
default file type is .HLB.
flags
OpenVMS usage:mask_longword
type: longword (unsigned)
access: read only
mechanism: by reference
Flags specifying help output options. Each programming language
provides an appropriate mechanism for accessing these flags.
The flags argument is the address of an unsigned longword that
contains the following flags, when set:
Flag Description
HLP$M_PROMPT Interactive help prompting is in effect.
HLP$M_ The process logical name table is searched for
PROCESS default help libraries.
HLP$M_GROUP The group logical name table is searched for group
default help libraries.
HLP$M_SYSTEM The system logical name table is searched for
system default help libraries.
HLP$M_ The list of default libraries available is output
LIBLIST with the list of topics available.
HLP$M_HELP The list of topics available in a help library is
preceded by the major portion of the text on help.
If you omit this longword, the default is for prompting and all
default library searching to be enabled, but no library list is
generated and no help text precedes the list of topics.
input_routine
OpenVMS usage:procedure
type: procedure value
access: read only
mechanism: by reference
Routine used for prompting. The input_routine argument is the
address of the procedure value of the prompting routine. You
should specify either the address of LIB$GET_INPUT or a routine
of your own that has the same calling format as LIB$GET_INPUT.
This argument must be supplied when the HELP command is run in
prompting mode (that is, HLP$M_PROMPT is set or defaulted).
3 – Description
The LBR$OUTPUT_HELP routine provides a simple, one-call method
to initiate an interactive help session. Help library bookkeeping
functions, such as LBR$INI_CONTROL and LBR$OPEN, are handled
internally. You should not call LBR$INI_CONTROL or LBR$OPEN
before you issue a call to LBR$OUTPUT_HELP.
LBR$OUTPUT_HELP accepts help keys in the same format as LBR$GET_
HELP, with the following qualifications:
o If the keyword HELP is supplied, help text on HELP is output,
followed by a list of HELP subtopics available.
If no help keys are provided or if the line_desc argument is
0, a list of topics available in the root library is output.
o If the line_desc argument contains a list of help keys, then
each key must be separated from its predecessor by a slash
(/) or by one or more spaces.
o The first key can specify a library to replace the main
library as the root library (the first library searched) in
which LBR$OUTPUT_HELP searches for help. A key used for this
purpose must have the form <@filespec>, where filespec is
subject to the same restrictions as the library_name argument.
If the specified library is an enabled user-defined default
library, then filespec can be abbreviated as any unique
substring of that default library's logical name translation.
In default library searches, you can define one or more default
libraries for LBR$OUTPUT_HELP to search for help information not
contained in the root library. Do this by equating logical names
(HLP$LIBRARY, HLP$LIBRARY_1, . . . ,HLP$LIBRARY_999) to the file
specifications of the default help libraries. You can define
these logical names in the process, group, or system logical name
table.
If default library searching is enabled by the flags argument,
LBR$OUTPUT_HELP uses those flags to determine which logical
name tables are enabled and then automatically searches any
user default libraries that have been defined in those logical
name tables. The library search order proceeds as follows: root
library, main library (if specified and different from the root
library), process libraries (if enabled), group libraries (if
enabled), system libraries (if enabled). If the requested help
information is not found in any of these libraries, LBR$OUTPUT_
HELP returns to the root library and issues a "help not found"
message.
To enter an interactive help session (after your initial request
for help has been satisfied), you must set the HLP$M_PROMPT bit
in the flags argument.
You can encounter four different types of prompt in an
interactive help session. Each type represents a different level
in the hierarchy of help available to you.
1. If the root library is the main library and you are not
currently examining HELP for a particular topic, the prompt
Topic? is output.
2. If the root library is a library other than the main library
and if you are not currently examining HELP for a particular
topic, a prompt of the form @<library-spec>Topic? is output.
3. If you are currently examining HELP for a particular topic
(and subtopics), a prompt of the form <keyword...>subtopic? is
output.
4. A combination of 2 and 3.
When you encounter one of these prompt messages, you can respond
in any one of several ways. Each type of response and its effect
on LBR$OUTPUT_HELP in each prompting situation is described in
the following table:
Action in the Current Prompt Environment
Response (Keyed to the prompt in the preceding list)
keyword [ . . . ] (1,2) Search all enabled libraries for these
keys.
(3,4) Search additional help for the current
topic (and subtopic) for these keys.
@filespec (1,2) Same as above, except that the root
[keyword[ . . . ]] library is the library specified by filespec.
If the specified library does not exist, treat
@filespec as a normal key.
(3,4) Same as above; treat @filespec as a
normal key.
? (1,2) Display a list of topics available in
the root library.
(3,4) Display a list of subtopics of the
current topic (and subtopics) for which help
exists.
Carriage Return (1) Exit from LBR$OUTPUT_HELP.
(2) Change root library to main library.
(3,4) Strip the last keyword from a list of
keys defining the current topic (and subtopic)
environment.
Ctrl/Z (1,2,3,4) Exit from LBR$OUTPUT_HELP.
4 – Condition Values Returned
LBR$_ILLINROU Input routine improperly specified or omitted.
LBR$_ILLOUTROU Output routine improperly specified or
omitted.
LBR$_NOHLPLIS Error. No default help libraries can be
opened.
LBR$_TOOMNYARG Error. Too many arguments were specified.
LBR$_USRINPERR Error. An error status was returned by the
user-supplied input routine.