GetOptions

http://www.perl.com/doc/manual/html/lib/Getopt/Long.html#EXAMPLES

GetOptions is called with a list of option-descriptions, each of which consists of two elements: the option specifier and the option linkage. The option specifier defines the name of the option and, optionally, the value it can take. The option linkage is usually a reference to a variable that will be set when the option is used. For example, the following call to GetOptions:

GetOptions("size=i" => \$offset);

will accept a command line option ``size'' that must have an integer value. With a command line of ``--size 24'' this will cause the variable $offset to get the value 24.

Alternatively, the first argument to GetOptions may be a reference to a HASH describing the linkage for the options, or an object whose class is based on a HASH. The following call is equivalent to the example above:

%optctl = ("size" => \$offset);
GetOptions(\%optctl, "size=i");

For the other options, the values for argument specifiers are:

!

Option does not take an argument and may be negated, i.e. prefixed by ``no''. E.g. ``foo!'' will allow --foo (with value 1) and -nofoo (with value 0). The option variable will be set to 1, or 0 if negated.

+

Option does not take an argument and will be incremented by 1 every time it appears on the command line. E.g. ``more+'', when used with --more --more --more, will set the option variable to 3 (provided it was 0 or undefined at first).

The + specifier is ignored if the option destination is not a SCALAR.

=s

Option takes a mandatory string argument. This string will be assigned to the option variable. Note that even if the string argument starts with - or --, it will not be considered an option on itself.

:s

Option takes an optional string argument. This string will be assigned to the option variable. If omitted, it will be assigned ``'' (an empty string). If the string argument starts with - or --, it will be considered an option on itself.

=i

Option takes a mandatory integer argument. This value will be assigned to the option variable. Note that the value may start with - to indicate a negative value.

:i

Option takes an optional integer argument. This value will be assigned to the option variable. If omitted, the value 0 will be assigned. Note that the value may start with - to indicate a negative value.

=f

Option takes a mandatory real number argument. This value will be assigned to the option variable. Note that the value may start with - to indicate a negative value.

:f

Option takes an optional real number argument. This value will be assigned to the option variable. If omitted, the value 0 will be assigned.

A lone dash - is considered an option, the corresponding option name is the empty string.

A double dash on itself -- signals end of the options list.