This is yet another alternative for parsing command line arguments in C++.
The main design criteria were:
- Fast to recompile the main. The library has very small footprint as regards to implicitly included headers. The main using this library includes indirectly only
stringandcstdint. - Easily allows validation of passed values.
- Ease of declaring options and accessing them.
- Requires C++11 or higher.
A simple example, without validation looks as follows:
#include <iostream>
#include "options/Parser.hpp"
int main(int argc, char *argv[])
{
Options::Parser args_parser;
args_parser.add_mandatory("config", 'c', "Configuration file"); // --config, -c
args_parser.add_optional("count", "Number of iterations", "10"); // --count
args_parser.add_optional("threshold", 't', "Some threshold", "3.14"); // --threshold, -t
args_parser.add_flag("help", 'h', "This help is accessible via short and long option");
using std::cout;
using std::endl;
if (!args_parser.parse(argc, argv) || args_parser.as_bool("help"))
{
cout << "Usage: " << argv[0] << " [options] [-- [positional arguments]]" << endl;
cout << args_parser.get_possible_options() << endl;
return -1;
}
// Print all options
cout << std::boolalpha;
cout << "Options:" << endl;
cout << " config : " << args_parser.as_string("config") << endl;
cout << " count : " << args_parser.as_int("count") << endl;
cout << " threshold : " << args_parser.as_double("threshold") << endl;
// positional arguments are all the strings after "--" separator, for example:
// ./example_simple -c config_file.txt -- these strings are positional arguments
if (args_parser.positional_count() > 0)
{
cout << "Positional parameters:" << endl;
for (size_t i = 0; i < args_parser.positional_count(); ++i)
cout << " [" << i << "]: " << args_parser.positional(i) << endl;
}
else
cout << "No positional parameters." << endl;
return 0;
}An example "session" on the console may look like this:
./build_example_debug/example_simple
Usage: ./build_example_debug/example_simple [options] [-- [positional arguments]]
-c, --config M Configuration file
--count Number of iterations (default: 10)
-t, --threshold Some threshold (default: 3.14)
-h, --help This help is accessible via short and long option
./build_example_debug/example_simple -c some_file.cfg -- this is a string
Options:
config : some_file.cfg
count : 10
threshold : 3.14
Positional parameters:
[0]: this
[1]: is
[2]: a
[3]: string
A similar example, but with data validation can be found in src/example.
This library can be used in a few ways:
Using cmake the easiest way seems to be using FetchContent mechanism:
include(FetchContent)
FetchContent_Declare(
options
GIT_REPOSITORY https://github.com/opokatech/options
GIT_TAG v3.0.0
GIT_SHALLOW TRUE
GIT_PROGRESS TRUE)
FetchContent_MakeAvailable(options)
# ....
add_executable(example my_main.cpp)
target_link_libraries(example PRIVATE options)Another option is to clone the whole repository as a git submodule
and add it via add_subdirectory:
git submodule add https://github.com/opokatech/options externals/options
# optionally checkout some particular version:
cd externals/options
git checkout v3.0.0And then in your CMakeLists.txt:
add_subdirectory(external/options) # location of the cloned repository
add_executable(example my_main.cpp)
target_link_libraries(example PRIVATE options)And there is of course the most simple and not recommended way:
copying src/options directory to your project and adding the files from it to
the compilation process. Either by hand OR by including only the options directory
via add_subdirectory. After all the whole library consists of just 7 files.
-
an option may have an argument or not. An option without an argument is a flag,
-
an option is always identified by a long name. A long name is used with 2 dashes in front of it, like so
--something. It may have a single character short version which is then used with a single dash in front of it, like so-s. -
an option can be mandatory - which means it must be specified,
-
it is not checked if the defined options are unique,
-
it is not checked if the default value passes the validation (if used).