user404d / cxxopts

Lightweight C++ command line option parser

Quick start

This is a lightweight C++ option parser library, supporting the standard GNU style syntax for options.

Options can be given as:

--long
--long=argument
--long argument
-a
-ab
-abc argument

where c takes an argument, but a and b do not.

Additionally, anything after -- will be parsed as a positional argument.

Basics

#include <cxxopts.hpp>

Create a cxxopts::Options instance.

cxxopts::Options options("MyProgram", "One line description of MyProgram");

Then use add_options.

options.add_options()
  ("d,debug", "Enable debugging")
  ("f,file", "File name", cxxopts::value<std::string>())
  ;

Options are declared with a long and an optional short option. A description must be provided. The third argument is the value, if omitted it is boolean. Any type can be given as long as it can be parsed, with operator>>.

To parse the command line do:

options.parse(argc, argv);

To retrieve an option use options.count("option") to get the number of times it appeared, and

options["opt"].as<type>()

to get its value. If "opt" doesn't exist, or isn't of the right type, then an exception will be thrown.

Help groups

Options can be placed into groups for the purposes of displaying help messages. To place options in a group, pass the group as a string to add_options. Then, when displaying the help, pass the groups that you would like displayed as a vector to the help function.

Positional Arguments

Positional arguments can be optionally parsed into one or more options. To set up positional arguments, call

options.parse_positional({"first", "second", "last"})

where "last" should be the name of an option with a container type, and the others should have a single value.

Default and implicit values

An option can be declared with a default or an implicit value, or both.

A default value is the value that an option takes when it is not specified on the command line. The following specifies a default value for an option:

cxxopts::value<std::string>()->default_value("value")

An implicit value is the value that an option takes when it is given on the command line without an argument. The following specifies an implicit value:

cxxopts::value<std::string>()->implicit_value("implicit")

If an option had both, then not specifying it would give the value "value", writing it on the command line as --option would give the value "implicit", and writing --option=another would give it the value "another".

Linking

This is a header only library.

Requirements

The only build requirement is a C++ compiler that supports C++11 regular expressions. For example GCC >= 4.9 or clang with libc++.

TODO list

• Allow unrecognised options.
• Various help strings.
• Unicode aware for help strings.