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jarro2783/cxxopts

★ 4,763C++Audience · developerComplexity · 2/5LicenseSetup · easy

TLDR

A single-header C++ library for parsing command-line flags and arguments, so you can add options like --verbose or --file to your program without writing the plumbing yourself.

Mindmap

mindmap
  root((cxxopts))
    What it does
      Parse CLI flags
      Typed values
      Auto help text
    Flag types
      Long flags
      Short flags
      Positional args
    Features
      Default values
      Option groups
      Exception handling
    Install
      Header only
      Homebrew
      vcpkg and Conan
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Things people build with this

USE CASE 1

Add --verbose, --output, and --count flags to a C++ command-line tool with automatic usage text generation.

USE CASE 2

Parse positional arguments alongside named flags so users can pass filenames without a flag prefix.

USE CASE 3

Group command-line options into labeled sections to produce an organized, readable --help message.

Tech stack

C++

Getting it running

Difficulty · easy Time to first run · 5min
MIT license, use freely for any purpose including commercial projects, with the copyright notice kept.

In plain English

cxxopts is a small C++ library that handles command line option parsing. When you write a program and want users to pass flags like --verbose or --file myfile.txt on the command line, this library takes care of reading and interpreting those inputs so you do not have to write that plumbing yourself. The library is header-only, which means you include a single .hpp file in your project and you are done. There is no separate compilation step or external dependency to link against. It follows the standard GNU-style syntax that most command line tools on Linux and macOS already use, so options like --long, --long=value, -a, and grouped short flags like -abc all work as expected. To use it, you create an Options object, add the flags your program accepts (each with a name, description, and optional type like int or string), then call parse with the standard argc and argv arguments your main function receives. After parsing, you can ask for how many times a flag appeared or retrieve its value cast to the correct type. If a flag is unknown or a value cannot be parsed, the library throws a typed exception with a readable message. The library also handles positional arguments, which are values passed without a flag name in front of them. You can collect them individually or gather all remaining ones into a list. Options can be given default values for when the user does not supply them, or implicit values for when a flag is present but no argument follows it. For help output, you can group options into named sections so the printed usage message is organized by category rather than dumped as a flat list. The project is MIT-licensed, available on Homebrew, Conan, and vcpkg, and is included in the Awesome C++ list.

Copy-paste prompts

Prompt 1
Using cxxopts, help me add --input and --output file path flags plus a --verbose boolean flag to my C++ main function.
Prompt 2
Show me how to define positional arguments with cxxopts so my program can accept a list of filenames without a flag prefix.
Prompt 3
Help me group cxxopts options into named sections so the --help output is organized by category instead of a flat list.
Prompt 4
Show me how to catch cxxopts parse exceptions and print a user-friendly error message when an unknown flag is passed.
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