base on Lightweight C++ command line option parser [](https://travis-ci.org/jarro2783/cxxopts) # Release versions Note that `master` is generally a work in progress, and you probably want to use a tagged release version. ## Version 3 breaking changes If you have used version 2, there are a couple of breaking changes in version 3 that you should be aware of. If you are new to `cxxopts` you can skip this section. The parser no longer modifies its arguments, so you can pass a const `argc` and `argv` and expect them not to be changed. The `ParseResult` object no longer depends on the parser. So it can be returned from a scope outside the parser and still work. Now that the inputs are not modified, `ParseResult` stores a list of the unmatched arguments. These are retrieved like follows: ```cpp auto result = options.parse(argc, argv); result.unmatched(); // get the unmatched arguments ``` # 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 ```cpp #include <cxxopts.hpp> ``` Create a `cxxopts::Options` instance. ```cpp cxxopts::Options options("MyProgram", "One line description of MyProgram"); ``` Then use `add_options`. ```cpp options.add_options() ("d,debug", "Enable debugging") // a bool parameter ("i,integer", "Int param", cxxopts::value<int>()) ("f,file", "File name", cxxopts::value<std::string>()) ("v,verbose", "Verbose output", cxxopts::value<bool>()->default_value("false")) ; ``` 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: ```cpp auto result = options.parse(argc, argv); ``` To retrieve an option use `result.count("option")` to get the number of times it appeared, and ```cpp result["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. ## Unrecognised arguments You can allow unrecognised arguments to be skipped. This applies to both positional arguments that are not parsed into another option, and `--` arguments that do not match an argument that you specify. This is done by calling: ```cpp options.allow_unrecognised_options(); ``` and in the result object they are retrieved with: ```cpp result.unmatched() ``` ## Exceptions Exceptional situations throw C++ exceptions. There are two types of exceptions: errors defining the options, and errors when parsing a list of arguments. All exceptions derive from `cxxopts::exceptions::exception`. Errors defining options derive from `cxxopts::exceptions::specification` and errors parsing arguments derive from `cxxopts::exceptions::parsing`. All exceptions define a `what()` function to get a printable string explaining the error. ## 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 are those given without a preceding flag and can be used alongside non-positional arguments. There may be multiple positional arguments, and the final positional argument may be a container type to hold a list of all remaining positionals. To set up positional arguments, first declare the options, then configure a set of those arguments as positional like: ```cpp options.add_options() ("script", "The script file to execute", cxxopts::value<std::string>()) ("server", "The server to execute on", cxxopts::value<std::string>()) ("filenames", "The filename(s) to process", cxxopts::value<std::vector<std::string>>()); options.parse_positional({"script", "server", "filenames"}); // Parse options the usual way options.parse(argc, argv); ``` For example, parsing the following arguments: ~~~ my_script.py my_server.com file1.txt file2.txt file3.txt ~~~ will result in parsed arguments like the following table: | Field | Value | | ------------- | ----------------------------------------- | | `"script"` | `"my_script.py"` | | `"server"` | `"my_server.com"` | | `"filenames"` | `{"file1.txt", "file2.txt", "file3.txt"}` | ## 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: ```cpp 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: ```cpp 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"`. Note that the default and implicit value is always stored as a string, regardless of the type that you want to store it in. It will be parsed as though it was given on the command line. Default values are not counted by `Options::count`. ## Boolean values Boolean options have a default implicit value of `"true"`, which can be overridden. The effect is that writing `-o` by itself will set option `o` to `true`. However, they can also be written with various strings using `=value`. There is no way to disambiguate positional arguments from the value following a boolean, so we have chosen that they will be positional arguments, and therefore, `-o false` does not work. ## `std::vector<T>` values Parsing a list of values into a `std::vector<T>` is also supported, as long as `T` can be parsed. To separate single values in a list the define symbol `CXXOPTS_VECTOR_DELIMITER` is used, which is ',' by default. Ensure that you use no whitespaces between values (unless the entire list is double quoted) because those would be interpreted as the next command line option. Example for a command line option that can be parsed as a `std::vector<double>`: ~~~ --my_list=1,-2.1,3,4.5 ~~~ If the list of values is quoted, then spaces can be included. For example: ~~~ --my_list="review,memory sanitize,build help,reformat" ~~~ This will be parsed into `review`, `memory sanitize`, `build help`, and `reformat`. ## Options specified multiple times The same option can be specified several times, with different arguments, which will all be recorded in order of appearance. An example: ~~~ --use train --use bus --use ferry ~~~ this is supported through the use of a vector of value for the option: ~~~ options.add_options() ("use", "Usable means of transport", cxxopts::value<std::vector<std::string>>()) ~~~ ## Custom help The string after the program name on the first line of the help can be completely replaced by calling `options.custom_help`. Note that you might also want to override the positional help by calling `options.positional_help`. ## Example Putting all together: ```cpp #include <iostream> #include "cxxopts.hpp" int main(int argc, char** argv) { cxxopts::Options options("test", "A brief description"); options.add_options() ("b,bar", "Param bar", cxxopts::value<std::string>()) ("d,debug", "Enable debugging", cxxopts::value<bool>()->default_value("false")) ("f,foo", "Param foo", cxxopts::value<int>()->default_value("10")) ("h,help", "Print usage") ; auto result = options.parse(argc, argv); if (result.count("help")) { std::cout << options.help() << std::endl; exit(0); } bool debug = result["debug"].as<bool>(); std::string bar; if (result.count("bar")) bar = result["bar"].as<std::string>(); int foo = result["foo"].as<int>(); return 0; } ``` # Linking This is a header only library. # Requirements The only build requirement is a C++ compiler that supports C++11 features such as: * regex * constexpr * default constructors GCC >= 4.9 or clang >= 3.1 with libc++ are known to work. The following compilers are known not to work: * MSVC 2013 ", Assign "at most 3 tags" to the expected json: {"id":"10655","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"