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The arg-optional
attribute indicates that the argument to the option is
optional (need not be specified on the command line). This is only valid if
the arg-type is string
(see arg-type string) or
keyword
(see arg-type keyword). If it is keyword
, then this
attribute may also specify the default keyword to assume when the argument is
not supplied. If left empty, arg-default (see arg-default) or the
zero-valued keyword will be used.
The syntax rules for identifying the option argument are:
=
), then everything after that character is the
option argument.
This is overridden and the options are required if the libopts library gets configured with --disable-optional-args.