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'])]).