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When guided, three predicates are called in the calling module. opt_type/3 must be defined, the others need not. Note that these three predicates may be defined as multifile to allow multiple modules contributing to the provided commandline options. Defining them as discontiguous allows for creating blocks that describe a group of related options.
-. A single character implies a short option, multiple a long option. Long options use
_as word separator, user options may use either
-. Type is one of:
nonneg|boolean, for an option
http(3000). With an optional boolean an option is considered boolean if it is the last or the next argument starts with a hyphen (
--opt=valuenotation. This explicit value specification converts
1and the obvious false equivalents to Prolog
false. If the option is specified, Default is used. If
--nooptis used, the inverse of Default is used.
integer. Requires value >= 0.
integer. Requires value >= 1.
float, else convert as
integer. Then check the range.
atom, but requires the value to be a member of List (enum type).
file, and check access using access_file/2. A value
-is not checked for access, assuming the application handles this as standard input or output.
directory, and check access. Access is one of
create. In the latter case the parent directory must exist and have write access.
term, but passes Options to term_string/3. If the option
variable_names(Bindings)is given the option value is set to the pair
--help are bound to help. If
opt_type(Opt, help, boolean) is true for some Opt, the default
help binding and help message are disabled and the normal user
rules apply. In particular, the user should also provide a rule for