boostprogramoptions

Boost.Program_options is a component of the Boost C++ Libraries that provides a framework for describing, parsing, and retrieving command-line options, configuration file options, and environment variables. It offers a type-safe interface for declaring allowable options using options_description, grouping them, and reading their values into a variables_map for use within the program. The library supports required options, default values, positional and named arguments, and integrates with Boost's type system via value semantics and validators.

Core concepts and workflow: An options_description collects the declared options, while a pos_options_description maps positional arguments. To read input, a variables_map is created, and parse_command_line or parse_config_file is used in combination with store, followed by notify to perform validations and conversions. Environment variables can be mapped to options through dedicated parsing. Options can be defined with types such as int or std::string, and may specify default_value, implicit_value for flags, and multi-value support via multitoken. The library also supports required() options and custom validators to enforce ranges or other constraints.

Usage and scope: Boost.Program_options is commonly used in C++ applications and tools that require flexible configuration through command-line arguments and config files. It is a Boost library that requires linking with the boost_program_options component. Typical usage includes a single, centralized definition of options that can be exposed to both CLI and configuration files, with values extracted into program variables via the variables_map. It remains a stable and widely adopted part of the Boost ecosystem.