Options

For this page, we will assume that there is a cxxopts::Options object declared like so:

cxxopts::Options options(argv[0]);

To add options to the parser, use the function add_options as in the following example:

options.add_options()("option", "description", value)

Where "option" describes the option, "description" is a description of the option for the help, and value is an object describing the type of the argument to the option.

Options

Options must have a long form, and may have a short form. To specify a command line option, the string "option" has the form:

l,long

where the l, is optional. This specifies an option whose long name is long, and whose short name is l.

Values

The parameters to arguments can be parsed, rather than just being recognised as a string. In addition, multiple occurrences of an option can be pushed into a vector. To specify a type for a parameter, the function cxxopts::value is used, which takes a template parameter specifying the type of a parameter, and an optional reference to a variable, into which the parsed value will be stored.

For example, the following example adds an option file, with a short option f, which takes a string:

options.add_options()
  ("f,file", "File", cxxopts::value<std::string>());

The next example adds an option verbose, with a short option v, and takes an integer which is parsed into a local variable:

int verbose = 0;
options.add_options()
  ("v,verbose", "Verbosity", cxxopts::value(verbose));

Options can be parsed into a vector, so that an option can appear multiple times on the command line. The following example adds the argument of each occurrence of --input to a vector:

std::vector<std::string> input;
options.add_options()
  ("i,input", "Input", cxxopts::value(input));