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3.1.3 The online help system

The online help system is invoked by the help command. ? may be used as a synonym for help. Simply typing help; displays the "top" of the help system (i.e., the title page of the SINGULAR manual) which offers a short table of contents. Typing help topic; shows the available documentation on the respective topic. Here, topic may be either a function name or, more generally, any index entry of the SINGULAR manual. Furthermore, topic may contain wildcard characters. See help, for more information.

Online help information can be displayed in various help browsers. The following table lists a summary of the browsers which are always present. Usually, external browsers are much more convenient: A complete, customizable list can be found in the file LIB/help.cnf.

Browser Platform Description
html Windows displays a html version of the manual in your default html browser
builtin all simply outputs the help information in plain ASCII format
emacs Unix, Windows when running SINGULAR within (X)emacs, displays help inside the (X)emacs info buffer.
dummy all displays an error message due to the non-availability of a help browser

External browsers depend on your system and the contents of LIB/help.cnf, the default includes: htmlview (displays HTML help pages via htlmview),
mac (displays HTML help pages via open),
mac-net (displays HTML help pages via open),
mozilla (displays HTML help pages via mozilla),
firefox (displays HTML help pages via firefox),
konqueror (displays HTML help pages via konqueror),
galeon (displays HTML help pages via galeon),
netscape (displays HTML help pages via netscape),
safari (displays HTML help pages on MacOsX via safari),
tkinfo (displays INFO help pages via tkinfo),
xinfo (displays INFO help pages via info),
info (displays INFO help pages via info),
lynx (displays HTML help pages via lynx).

The browser which is used to display the help information, can be either set at startup time with the command line option (see Command line options)
or with the SINGULAR command (see system)
system("--browser", "");
The SINGULAR command
lists all available browsers and the command
returns the currently used browser.

If no browser is explicitly set by the user, then the first available browser (w.r.t. the order of the browsers in the file LIB/help.cnf) is chosen.

The .singularrc (see Startup sequence) file is a good place to set your default browser. Recall that if a file $HOME/.singularrc exists on your system, then the content of this file is executed before the first user input. Hence, putting
if (! system("--emacs"))
  // only set help browser if not running within emacs
  system("--browser", "info");
// if help browser is later on set to a web browser,
// allow it to fetch HTML pages from the net
system("--allow-net", 1);
in your file $HOME/.singularrc sets your default browser to info, unless SINGULAR is run within emacs (in which case the default browser is automatically set to emacs).

Obviously, certain external files and programs are required for the SINGULAR help system to work correctly. If something is not available or goes wrong, here are some tips for troubleshooting the help system:

  • Under Unix, the environment variable DISPLAY has to be set for all X11 browsers to work.

  • The help browsers are only available if the respective programs are installed on your system (for xinfo, the programs xterm and info are necessary). You can explicitly specify which program to use, by changing the entry in LIB/help.cnf

  • If the help browser cannot find the local html pages of the SINGULAR manual (which it will look for at $RootDir/html -- see Loading a library for more info on $RootDir) and the (command-line) option --allow-net has explicitly been set (see Command line options and system for more info on setting values of command-line options), then it dispatches the html pages from (Note that the non-local net-access of HTML pages is disabled, by default.)
    An alternative location of a local directory where the html pages reside can be specified by setting the environment variable SINGULAR_HTML_DIR.

  • The info based help browsers tkinfo, xinfo, info, and builtin need the (info) file which will be looked for at $RootDir/info/ (see Loading a library for more info on $RootDir). An alternative location of the info file of the manual can be specified by setting the environment variable SINGULAR_INFO_FILE.

Command line options

Info help browsers

The help browsers tkinfo, xinfo and info (so-called info help browsers) are based on the info program from the GNU texinfo package. See section `Getting started' in The Info Manual, for more information.

For info help browsers, the online manual is decomposed into "nodes" of information, closely related to the division of the printed manual into sections and subsections. A node contains text describing a specific topic at a specific level of detail. The top line of a node is its "header". The node's header tells the name of the current node (Node:), the name of the next node (Next:), the name of the previous node (Prev:), and the name of the upper node (Up:).

To move within info, type commands consisting of single characters. Do not type RETURN. Do not use cursor keys, either. Using some of the cursor keys by accident might pop to some totally different node. Type l to return to the original node. Some of the info commands read input from the command line at the bottom. The TAB key may be used to complete partially entered input.

The most important commands are:

leaves the online help system
goes to the next node
goes to the previous node
goes to the upper node
picks a menu item specified by name
follows a cross reference
goes to the previously visited node
goes to the beginning of the current node
goes to the end of the current node
scrolls forward a page
scrolls backward a page
invokes info tutorial (use l to return to the manual or CTRL-X 0 to remove extra window)
shows a short overview over the online help system (use l to return to the manual or CTRL-X 0 to remove extra window)
searches through the manual for a specific string, and selects the node in which the next occurrence is found
1, ..., 9
picks i-th subtopic from a menu

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