102 lines
2.9 KiB
Markdown
102 lines
2.9 KiB
Markdown
[](https://travis-ci.org/jarro2783/cxxopts)
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# Quick start
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This is a lightweight C++ option parser library, supporting the standard GNU
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style syntax for options.
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Options can be given as:
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--long
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--long=argument
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--long argument
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-a
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-ab
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-abc argument
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where c takes an argument, but a and b do not.
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Additionally, anything after `--` will be parsed as a positional argument.
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## Basics
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#include <cxxopts.hpp>
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Create a cxxopts::Options instance.
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cxxopts::Options options("MyProgram", "One line description of MyProgram");
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Then use `add_options`.
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options.add_options()
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("d,debug", "Enable debugging")
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("f,file", "File name", cxxopts::value<std::string>())
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;
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Options are declared with a long and an optional short option. A description
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must be provided. The third argument is the value, if omitted it is boolean.
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Any type can be given as long as it can be parsed, with operator>>.
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To parse the command line do:
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options.parse(argc, argv);
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To retrieve an option use `options.count("option")` to get the number of times
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it appeared, and
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options["opt"].as<type>()
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to get its value. If "opt" doesn't exist, or isn't of the right type, then an
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exception will be thrown.
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## Help groups
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Options can be placed into groups for the purposes of displaying help messages.
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To place options in a group, pass the group as a string to `add_options`. Then,
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when displaying the help, pass the groups that you would like displayed as a
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vector to the `help` function.
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## Positional Arguments
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Positional arguments can be optionally parsed into one or more options.
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To set up positional arguments, call
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options.parse_positional({"first", "second", "last"})
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where "last" should be the name of an option with a container type, and the
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others should have a single value.
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## Default and implicit values
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An option can be declared with a default or an implicit value, or both.
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A default value is the value that an option takes when it is not specified
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on the command line. The following specifies a default value for an option:
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cxxopts::value<std::string>()->default_value("value")
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An implicit value is the value that an option takes when it is given on the
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command line without an argument. The following specifies an implicit value:
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cxxopts::value<std::string>()->implicit_value("implicit")
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If an option had both, then not specifying it would give the value `"value"`,
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writing it on the command line as `--option` would give the value `"implicit"`,
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and writing `--option=another` would give it the value `"another"`.
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# Linking
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This is a header only library.
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# Requirements
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The only build requirement is a C++ compiler that supports C++11 regular
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expressions. For example GCC >= 4.9 or clang with libc++.
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# TODO list
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* Allow unrecognised options.
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* Various help strings.
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* Unicode aware for help strings.
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