CLI11, a powerful library for writing command line interfaces in C++11, has just
been released. There are no requirements beyond C++11 support (and even
<regex> support not required). It works on Mac, Linux, and Windows, and has
100% test coverage on all three systems. You can simply drop in a single header
file (CLI11.hpp available in releases) to use CLI11 in your own application.
Other ways to integrate it into a build system are listed in the README.
The library was inspired the Python libraries Plumbum and Click, and incorporates many of their user friendly features. The library is extensively documented, with a friendly introduction, a tutorial filled (in progress) GitBook, and more technical API docs.
The syntax is simple and scales from a basic application to a massive physics analysis with multiple models and many parameters and switches. For example, this is a simple program that has an optional parameter that defaults to 1:
./a.out
Parameter value: 0
./a.out -p 4
Parameter value: 4
./a.out --help
App description
Usage: ./a.out [OPTIONS]
Options:
-h,--help Print this help message and exit
-p INT Parameter
Like any good command line application, help is provided. This program can be implemented in under 15 lines:
#include "CLI11.hpp"
#include <iostream>
int main(int argc, char **argv) {
CLI::App app{"App description"};
// Define options
int p = 0;
app.add_option("-p", p, "Parameter");
// Standard parsing lines (copy and paste in)
try {
app.parse(argc, argv);
} catch (const CLI::ParseError &e) {
return app.exit(e);
}
std::cout << "Parameter value: " << p << std::endl;
return 0;
}
Unlike some other libraries, this is enough to exit correctly and cleanly if help is requested or if incorrect arguments are passed. You can try this example out for yourself. To compile with GCC:
g++ -std=c++11 main.cpp
Much more complicated options are handled elegantly:
std::string req_real_file;
app.add_option("-f,--file", file, "Require an existing file")
->required()
->check(CLI::ExistingFile);
You can use any valid type; the above example could have used a
boost::file_system file instead of a std::string. The value is a real value
and does not require any special lookups to access. You do not have to risk
typos by repeating the values after parsing like some libraries require. The
library also handles positional arguments, flags, fixed or unlimited repeating
options, interdependent options, flags, custom validators, help groups, and
more.
You can use subcommands, as well. Subcommands support callback lambda functions
when parsed, or they can be checked later. You can infinitely nest subcommands,
and each is a full App instance, supporting everything listed above.
Reading/producing .ini files for configuration is also supported, as is using
environment variables as input. The base App can be subclassed and customized
for use in a toolkit (like GooFit). All the standard shell idioms, like --,
work as well.
CLI11 was developed at the University of Cincinnati to support of the GooFit library under NSF Award 1414736. It was recently featured in a DIANA/HEP meeting at CERN. Please give it a try! Feedback is always welcome.