μopt / muopt

muopt is a header-only C++17 micro-library for argument parsing. Its design is inspired by Lexopt.

Features

The following command line options are supported.

• Short arguments (-h)
• Long arguments (--help)
• Short arguments with values (-ovalue, -o=value, -o value)
• Chained short arguments (-abc results three short flags: a, b, and c)
• Long arguments with values (--name=Vito, --name Vito)
• Plain arguments, i.e. options without hyphen prefixes (run, build)

Examples

#include "muopt/muopt.hpp"
#include <iostream>

int main(int argc, char **argv) {
  muopt::Parser parser(argc, argv);

  while (std::optional<muopt::Arg> arg = parser.next()) {
    if (arg->is_long("help"))
      std::cout << "usage: example [--input FILE]\n";
    if (arg->is_long("input"))
      std::cout << parser.arg_value().value_or("") << '\n';
  }
}

See the examples directory for more usage examples.

Design

In muopt, options are values are both just arguments. Whether it is treated as an option or a value depends on how it interacts with the parser, the - and -- prefix determines the kind and not some coupling implementation.

1. The parser is created by instantiating muopt::Parser with argc and argv.
2. next() returns the next argument as a Short, Long, or Plain.
3. next() returns std::nullopt when args are exhausted.
4. arg_value() returns the string of the next Plain, if a Plain is next in line, consuming it and making it unavailable to the next next() call.
5. arg_value() returns std::nullopt otherwise. The non-Plain argument is not consumed; the next next() call will still see it.

Integration

CMake (FetchContent)

include(FetchContent)
FetchContent_Declare(
    muopt
    GIT_REPOSITORY https://github.com/secona/muopt.git
    GIT_TAG main
)
FetchContent_MakeAvailable(muopt)
target_link_libraries(program PRIVATE muopt::muopt)

CMake (vendored)

add_subdirectory(vendor/muopt)
target_link_libraries(program PRIVATE muopt::muopt)

Bazel (Bzlmod)

# in MODULE.bazel

bazel_dep(name = "muopt")

git_override(
    module_name = "muopt",
    commit = "bedd3f76720c9790b0fd3175f8e28eaab3c3c13e", # change as needed
    remote = "https://github.com/secona/muopt.git",
)

Bazel

new_git_repository(
    name = "muopt",
    commit = "bedd3f76720c9790b0fd3175f8e28eaab3c3c13e", # change as needed
    init_submodules = False,
    remote = "https://github.com/secona/muopt.git",
)

Motivation

In one of my Rust projects, I used Lexopt and loved it. When working on a C++ project, I tried looking for similar argument parsers with Lexopt's simplicity and couldn't find one, so I decided to make my own. muopt offers more control and is intended to be minimal, bare-bones, and without bloat.

License

muopt is licensed under the MIT License. See LICENSE for more information.

Acknowledgements

• lexopt for the inspiration.