Description

The ahelp command accesses the CIAO on-line documentation. By default it displays an ASCII version of the help file. The CIAO site contains HTML versions of the help files, which are also available on the European mirror site.

Finding help for a given subject

The help files are arranged by subject into contexts (both subject and context are a single word) and you access these files by either:

  unix% ahelp <subject>

or

  unix% ahelp <context> <subject>

depending on whether or not there are help files with the same subject but different contexts (ahelp will tell you if you need to specify a context). The ahelp tool is case insensitive when it comes to matching the subject and context values.

Searching for help

If you do not know the exact subject (for a tool, the subject is just the tool name), then you enter

  unix% about <keyword>

for a list of subjects related to your query (ie whatever value you use for <keyword>). To find out all the entries for a given context you use

  unix% ahelp -c <context>

If a search only returns one match then that page is automatically displayed, otherwise you will see a list of subjects, with context and synopsis, that match the search.

Using regular expressions

It is possible to use a regular expression when specifying any of the subject, context, or keyword in a search. To find a list of all the keywords that contain the text "par":

  unix% ahelp /par/

and to list all help files with contexts that begin with "sl":

  unix% ahelp -c /^sl/

This feature can be very useful when trying to search for help on a particular subject, since

  unix% about /bin/

will list all help files whose references include the text "bin" (so this would match bin, rebin, and binned amongst others).

There are a number of resources that describe the extended regular expression syntax used here, depending on what system you are using, such as "man regexp".

Listing specific sections of the help file

The "-b blockname" option is used to restrict the output to a given section of the help file. This can be useful if you only need specific information, such as the list of known bugs, description of a specific parameter, or the syntax of a given command.

Allowed values for the "-b blockname" option

It is not guaranteed that a help file will contain all these sections. The "Structure of a help file" section at the end of this file provides more details on what is included in a help file.

Command-line options

The most useful options are given below. If no option is supplied, ahelp defaults to -l.

Options for the CIAO developer

There are several other options that are only useful to CIAO developers and those that install the CIAO software.

Configuring ahelp

Ahelp uses the PAGER environment variable to find the program to use to page the ASCII output to the screen: examples of suitable values are more or "less -s".

If you make use of the "-b" option in ahelp a lot it may be worth setting up aliases for them. For instance, the following csh/tcsh commands

  unix% alias bugs     'ahelp -b BUGS '
  unix% alias params   'ahelp -b PARAM '
  unix% alias examples 'ahelp -b QEXAMPLELIST '

provide easy access to the bugs, parameter, and examples section of a help file - if they exists - by saying "bugs dmstat", "params aconvolve" ("params -t kernelspaec aconvolve" to list an individual parameter), or "examples dmfilth".