ArgsP

Simple arguments parser for C++20.

Usage

• Exceptions

   // In this example, all errors are thrown as exceptions.
  
   #include <ArgsP.hpp>
   #include <iostream>
   #include <iomanip>
  
   int main(int argc, char** argv)
   {
   	using namespace SCT::ArgsP;
  
   	// first parameter is prefix symbol count
   	Parameters::Int64 res_h({Base::Info{1, "h"}});
   	// default value
   	Parameters::Int64 res_w({{1, "w"}}, 100);
   	// multiple names for same flag
   	Flag::Bool help({{1, "h"}, {2, "help"}});
   	// capture argument without flag or parameter prefix
   	Arguments::String path = "/tmp/test.html";
  
   	// prefix symbol is '-'
   	Parser p = '-';
   	p.add_arguments(help, path, res_w, res_h);
  
   	auto program = p.parse(argc, argv);
   	std::cout << *program << ":\n";
   	std::cout << "  help(bool):   " << *help << '\n';
   	std::cout << "  path(string): " << std::quoted(*path) << '\n';
   	std::cout << "  res_w(int):   " << *res_w << '\n';
   	std::cout << "  res_h(int):   " << *res_h << '\n';
   	std::cout << '\n';
  
   	return 0;
   }

• Error code

   // ...
  
   // If the no-exceptions compile flag is used,
   // this parameter is always false.
   Parser p('-', false);
   p.add_arguments(help, path, res_w, res_h);
  
   auto program = p.parse(argc, argv);
   if (p.error())
   {
   	// ArgsP::Error::Exception is a subclass of std::system_error
   	const ArgsP::Error::Exception& ex = p.get_error_container().get_error();
  
   	// Print error
   	if (error.argument.size()) // maybe ""
   		std::cout << error.argument << '=';
   	std::cout << std::quoted(error.value);
   	std::cout << ": " << error.code().message() << '\n';
   	// Or use std::exception::what();
   	std::cout << "what(): " << error.what() << '\n';
  
   	return 1;
   }
  
   std::cout << *program << ":\n";
   std::cout << "  help(bool):   " << *help << '\n';
   std::cout << "  path(string): " << std::quoted(*path) << '\n';
   std::cout << "  res_w(int):   " << *res_w << '\n';
   std::cout << "  res_h(int):   " << *res_h << '\n';
   std::cout << '\n';
  
   return 0;
   // ...

Execution examples:

• $ ./test --help
  ./test:
    help(bool):   1
    path(string): "/tmp/test.html"
    res_w(int):   100
    res_h(int):   0
  

• $ ./test -h /test
  ./test:
    help(bool):   1
    path(string): "/test"
    res_w(int):   100
    res_h(int):   0
  

• $ ./test /test -w=10 -h 600
  ./test:
    help(bool):   0
    path(string): "/test"
    res_w(int):   10
    res_h(int):   600
  

Download or Install

• You can download one header version!

• Debian package available on releases

   $ curl -o ArgsP.deb -L $URL
   # dpkg -i ArgsP.deb

• ArchLinux package available on AUR

   $ yay -S sct_argsp

Adding a custom parameter/argument

• Simple and flexible approach (passing a function for standard types)

   #include <ArgsP.hpp>
  
   namespace ArgsP = SCT::ArgsP;
  
   struct Resolution
   {
       int width, height;
   };
  
   // Creates a function for parsing a string to value
   ArgsP::Error::Code parse_resolution(Resolution& value, std::string_view new_value)
   {
   	auto i = new_value.find('x');
   	if (i == new_value.npos) // Returns an error if 'x' symbol is missing
   		return ArgsP::Error::Code::syntax_error;
  
   	// Uses alternative to std::stoi. Doesn't throw errors;
   	// just returns either error or a value
   	auto width = ArgsP::str_to<uint32_t>(new_value.substr(0, i));
   	if (!width.has_value())
   		return width.error();
  
   	auto height = ArgsP::str_to<uint32_t>(new_value.substr(i + 1));
   	if (!height)
   		return height.error();
  
   	value.width = width.value_or(0);
   	value.height = height.value_or(0);
  
   	return ArgsP::Error::Code::no_error;
   }
  
   // Uses the default Parameter/Argument implementation and parse function
   using ResolutionParameter = ArgsP::Base::Parameter<Resolution, &parse_resolution>;
   using ResolutionArgument = ArgsP::Base::Argument<Resolution, &parse_resolution>;
  
   // ...

• Less flexible approach (creating a subclass with custom parsing logic)

   // ...
  
   // Creates subclass of default Parameter
   struct ResolutionParameter : ArgsP::Base::Parameter<Resolution>
   {
   	ResolutionParameter(Infos names, Resolution base = {100, 100})
   		: ArgsP::Base::Parameter<Resolution>(names, base) {}
  
   	// Overrides the 'parse_value' method to parse the resolution
   	// Default 'parse_value' tries to call the parse function
   	ArgsP::Error::Code parse_value(std::string_view new_value) override
   	{
   		auto i = new_value.find('x');
   		if (i == new_value.npos)
   			return ArgsP::Error::Code::syntax_error;
  
   		auto width = ArgsP::str_to<uint32_t>(new_value.substr(0, i));
   		if (!width)
   			return width.error();
  
   		auto height = ArgsP::str_to<uint32_t>(new_value.substr(i + 1));
   		if (!height)
   			return height.error();
  
   		// 'p_value' is defined in the parent class.
   		p_value.width = width.value_or(0);
   		p_value.height = height.value_or(0);
  
   		return ArgsP::Error::Code::no_error;
   	}
   };
  
   // ...

TODO

• Add RPM package
• Add Arch package