go-flags

Package flags provides an extensive command line option parser. The flags package is similar in functionality to the go built-in flag package but provides more options and uses reflection to provide a convenient and succinct way of specifying command line options. The following features are supported in go-flags: Additional features specific to Windows: The flags package uses structs, reflection and struct field tags to allow users to specify command line options. This results in very simple and concise specification of your application options. For example: This specifies one option with a short name -v and a long name --verbose. When either -v or --verbose is found on the command line, a 'true' value will be appended to the Verbose field. e.g. when specifying -vvv, the resulting value of Verbose will be {[true, true, true]}. Slice options work exactly the same as primitive type options, except that whenever the option is encountered, a value is appended to the slice. Map options from string to primitive type are also supported. On the command line, you specify the value for such an option as key:value. For example Then, the AuthorInfo map can be filled with something like -a name:Jesse -a "surname:van den Kieboom". Finally, for full control over the conversion between command line argument values and options, user defined types can choose to implement the Marshaler and Unmarshaler interfaces. The following is a list of tags for struct fields supported by go-flags: Either the `short:` tag or the `long:` must be specified to make the field eligible as an option. Option groups are a simple way to semantically separate your options. All options in a particular group are shown together in the help under the name of the group. Namespaces can be used to specify option long names more precisely and emphasize the options affiliation to their group. There are currently three ways to specify option groups. The flags package also has basic support for commands. Commands are often used in monolithic applications that support various commands or actions. Take git for example, all of the add, commit, checkout, etc. are called commands. Using commands you can easily separate multiple functions of your application. There are currently two ways to specify a command. The most common, idiomatic way to implement commands is to define a global parser instance and implement each command in a separate file. These command files should define a go init function which calls AddCommand on the global parser. When parsing ends and there is an active command and that command implements the Commander interface, then its Execute method will be run with the remaining command line arguments. Command structs can have options which become valid to parse after the command has been specified on the command line. It is currently not valid to specify options from the parent level of the command after the command name has occurred. Thus, given a top-level option "-v" and a command "add": go-flags has builtin support to provide bash completion of flags, commands and argument values. To use completion, the binary which uses go-flags can be invoked in a special environment to list completion of the current command line argument. It should be noted that this `executes` your application, and it is up to the user to make sure there are no negative side effects (for example from init functions). Setting the environment variable `GO_FLAGS_COMPLETION=1` enables completion by replacing the argument parsing routine with the completion routine which outputs completions for the passed arguments. The basic invocation to complete a set of arguments is therefore: where `completion-example` is the binary, `arg1` and `arg2` are the current arguments, and `arg3` (the last argument) is the argument to be completed. If the GO_FLAGS_COMPLETION is set to "verbose", then descriptions of possible completion items will also be shown, if there are more than 1 completion items. To use this with bash completion, a simple file can be written which calls the binary which supports go-flags completion: Completion requires the parser option PassDoubleDash and is therefore enforced if the environment variable GO_FLAGS_COMPLETION is set. Customized completion for argument values is supported by implementing the flags.Completer interface for the argument value type. An example of a type which does so is the flags.Filename type, an alias of string allowing simple filename completion. A slice or array argument value whose element type implements flags.Completer will also be completed.
1 version
Latest release: over 10 years ago

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