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134 lines
4.8 KiB
134 lines
4.8 KiB
go-flags: a go library for parsing command line arguments
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=========================================================
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[](https://godoc.org/github.com/jessevdk/go-flags) [](https://travis-ci.org/jessevdk/go-flags) [](https://coveralls.io/r/jessevdk/go-flags?branch=master)
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This library provides similar functionality to the builtin flag library of
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go, but provides much more functionality and nicer formatting. From the
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documentation:
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Package flags provides an extensive command line option parser.
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The flags package is similar in functionality to the go builtin flag package
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but provides more options and uses reflection to provide a convenient and
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succinct way of specifying command line options.
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Supported features:
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* Options with short names (-v)
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* Options with long names (--verbose)
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* Options with and without arguments (bool v.s. other type)
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* Options with optional arguments and default values
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* Multiple option groups each containing a set of options
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* Generate and print well-formatted help message
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* Passing remaining command line arguments after -- (optional)
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* Ignoring unknown command line options (optional)
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* Supports -I/usr/include -I=/usr/include -I /usr/include option argument specification
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* Supports multiple short options -aux
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* Supports all primitive go types (string, int{8..64}, uint{8..64}, float)
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* Supports same option multiple times (can store in slice or last option counts)
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* Supports maps
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* Supports function callbacks
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* Supports namespaces for (nested) option groups
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The flags package uses structs, reflection and struct field tags
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to allow users to specify command line options. This results in very simple
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and concise specification of your application options. For example:
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```go
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type Options struct {
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Verbose []bool `short:"v" long:"verbose" description:"Show verbose debug information"`
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}
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```
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This specifies one option with a short name -v and a long name --verbose.
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When either -v or --verbose is found on the command line, a 'true' value
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will be appended to the Verbose field. e.g. when specifying -vvv, the
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resulting value of Verbose will be {[true, true, true]}.
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Example:
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--------
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```go
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var opts struct {
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// Slice of bool will append 'true' each time the option
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// is encountered (can be set multiple times, like -vvv)
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Verbose []bool `short:"v" long:"verbose" description:"Show verbose debug information"`
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// Example of automatic marshalling to desired type (uint)
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Offset uint `long:"offset" description:"Offset"`
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// Example of a callback, called each time the option is found.
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Call func(string) `short:"c" description:"Call phone number"`
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// Example of a required flag
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Name string `short:"n" long:"name" description:"A name" required:"true"`
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// Example of a value name
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File string `short:"f" long:"file" description:"A file" value-name:"FILE"`
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// Example of a pointer
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Ptr *int `short:"p" description:"A pointer to an integer"`
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// Example of a slice of strings
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StringSlice []string `short:"s" description:"A slice of strings"`
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// Example of a slice of pointers
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PtrSlice []*string `long:"ptrslice" description:"A slice of pointers to string"`
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// Example of a map
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IntMap map[string]int `long:"intmap" description:"A map from string to int"`
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}
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// Callback which will invoke callto:<argument> to call a number.
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// Note that this works just on OS X (and probably only with
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// Skype) but it shows the idea.
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opts.Call = func(num string) {
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cmd := exec.Command("open", "callto:"+num)
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cmd.Start()
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cmd.Process.Release()
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}
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// Make some fake arguments to parse.
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args := []string{
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"-vv",
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"--offset=5",
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"-n", "Me",
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"-p", "3",
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"-s", "hello",
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"-s", "world",
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"--ptrslice", "hello",
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"--ptrslice", "world",
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"--intmap", "a:1",
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"--intmap", "b:5",
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"arg1",
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"arg2",
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"arg3",
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}
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// Parse flags from `args'. Note that here we use flags.ParseArgs for
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// the sake of making a working example. Normally, you would simply use
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// flags.Parse(&opts) which uses os.Args
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args, err := flags.ParseArgs(&opts, args)
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if err != nil {
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panic(err)
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}
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fmt.Printf("Verbosity: %v\n", opts.Verbose)
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fmt.Printf("Offset: %d\n", opts.Offset)
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fmt.Printf("Name: %s\n", opts.Name)
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fmt.Printf("Ptr: %d\n", *opts.Ptr)
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fmt.Printf("StringSlice: %v\n", opts.StringSlice)
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fmt.Printf("PtrSlice: [%v %v]\n", *opts.PtrSlice[0], *opts.PtrSlice[1])
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fmt.Printf("IntMap: [a:%v b:%v]\n", opts.IntMap["a"], opts.IntMap["b"])
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fmt.Printf("Remaining args: %s\n", strings.Join(args, " "))
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// Output: Verbosity: [true true]
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// Offset: 5
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// Name: Me
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// Ptr: 3
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// StringSlice: [hello world]
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// PtrSlice: [hello world]
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// IntMap: [a:1 b:5]
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// Remaining args: arg1 arg2 arg3
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```
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More information can be found in the godocs: <http://godoc.org/github.com/jessevdk/go-flags>
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