3.1.1 Options

The options processed by Gcal can be grouped into four major option classes. The options of the common option class are the standard options all GNU software should implement at least partially. The global option class contains options which affect the program output. The options of the calendar option class control the calendar layout, and the options of the fixed date option class control the fixed date layout and intensity.

Gcal supports both short-style options and GNU long-style options. Traditional short-style options are indicated by a single switch character, and trailed by the option character itself and perhaps a modifier or an argument. The most single character options⁸ can be composed into a single command line word: -Ax is equivalent to -A -x. GNU long-style options are indicated with ‘--’, and trailed by the mnemonic option name itself and perhaps an argument. Long-style options and their arguments may be abbreviated if done unambiguously. When a long-style option takes an argument, connect the option name and the argument with ‘=’.

Brackets ([ and ]) indicate in the following tables, that an option takes an optional argument. The ‘|’ character is used to separate several arguments from each other.

Gcal processes the GNU long-style options in a special, non-standard way. There are five different types of long-style options:

1. --foo
   Enables option --foo.
2. --foo=bar
   Enables option --foo with the required argument bar.
3. --foo[=bar[|…|bar]]
   Option --foo may have one bar argument. If no argument list is given, any argument can be given to this option. If an argument list is given, exactly one bar argument may be selected from the given list. If there is no argument chosen in this case, the first bar argument of the argument list is preselected by default.
4. --foo=bar|…|bar
   Option --foo requires exactly one bar argument which must be selected from the given argument list.
5. --foo=bar|…|bar|baz
   Option --foo requires exactly one bar argument which must be selected from the given bar argument list, or the alternative baz argument.

Traditional short-style options differ as follows:

1. -x
   Enables option -x.
2. -x bar
   Enables option -x with the required argument bar. The bar argument may be separated by a leading whitespace character from the short-style option character x. This means, the following notations are valid for giving an argument, namely -x bar or -xbar.
3. -x[bar|…|bar]
   Option -x may have one or more bar modifier. In this sense, modifiers are one or more characters which define a special mode of operation enabled by the -x option. A modifier may not be separated by a leading whitespace character from the short-style option character.