Use print_message/2 to print a usage message at Level. To print the
message as plain text indefault color, use debug. Other meaningful
options are informational or warning. The help page consists of
four sections, two of which are optional:
- The header is created from
opt_help(help(header), String).
It is optional.
- The usage is added by default. The part behind
Usage: <command> is by default [options] and can be
overruled using opt_help(help(usage), String).
- The actual option descriptions. The options are presented
in the order they are defined in opt_type/3. Subsequent
options for the same destination (option name) are joined
with the first.
- The footer_ is created from
opt_help(help(footer), String).
It is optional.
The help provided by help(header), help(usage) and help(footer) are
either a simple string or a list of elements as defined by
print_message_lines/3. In the latter case, the construct \Callable
can be used to call a DCG rule in the module from which the user
calls argv_options/3. For example, we can add a bold title using
opt_help(help(header), [ansi(bold, '~w', ['My title'])]).