### Install Kingpin

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Install Kingpin using the go get command.

```bash
$ go get gopkg.in/alecthomas/kingpin.v2
```

--------------------------------

### Simple Kingpin Example

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

A basic example demonstrating how to define and parse a boolean flag and a required string argument.

```go
var (
  verbose = kingpin.Flag("verbose", "Verbose mode.").Short('v').Bool()
  name    = kingpin.Arg("name", "Name of user.").Required().String()
)

func main() {
  kingpin.Parse()
  fmt.Printf("%v, %s\n", *verbose, *name)
}
```

--------------------------------

### Install Kingpin v1

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Use 'go get' to install the older stable version of Kingpin.

```sh
$ go get gopkg.in/alecthomas/kingpin.v1
```

--------------------------------

### Example CLI Help Output

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Demonstrates the default help message format generated by Kingpin for a sample CLI application, showing usage, flags, and commands.

```bash
$ go run ./examples/curl/curl.go --help
usage: curl [<flags>] <command> [<args> ...]

An example implementation of curl.

Flags:
  --help            Show help.
  -t, --timeout=5s  Set connection timeout.
  -H, --headers=HEADER=VALUE
                    Add HTTP headers to the request.

Commands:
  help [<command>...]
    Show help.

  get url <url>
    Retrieve a URL.

  get file <file>
    Retrieve a file.

  post [<flags>] <url>
    POST a resource.
```

--------------------------------

### Install CLI Tool Completion via Bash Profile

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Instructs users to add a statement to their bash_profile to enable shell completion for the CLI tool.

```bash
eval "$(your-cli-tool --completion-script-bash)"
```

```bash
eval "$(your-cli-tool --completion-script-zsh)"
```

--------------------------------

### Compile BOS CMD

Source: https://github.com/baidubce/bce-cmd/blob/master/README.md

Compiles the BOS CMD tool. Ensure Go (version 1.11+) is installed and GOROOT is configured.

```shell
sh build.sh
```

--------------------------------

### Simple Flag and Argument Parsing

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Demonstrates basic command-line application structure with flags and arguments using Kingpin. Useful for simple utilities.

```go
package main

import (
  "fmt"

  "gopkg.in/alecthomas/kingpin.v2"
)

var (
  debug   = kingpin.Flag("debug", "Enable debug mode.").Bool()
  timeout = kingpin.Flag("timeout", "Timeout waiting for ping.").Default("5s").OverrideDefaultFromEnvar("PING_TIMEOUT").Short('t').Duration()
  ip      = kingpin.Arg("ip", "IP address to ping.").Required().IP()
  count   = kingpin.Arg("count", "Number of packets to send").Int()
)

func main() {
  kingpin.Version("0.0.1")
  kingpin.Parse()
  fmt.Printf("Would ping: %s with timeout %s and count %d\n", *ip, *timeout, *count)
}
```

--------------------------------

### Complex Command-Line Application with Sub-commands

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Illustrates building a complex CLI application with global flags, sub-commands, and per-subcommand flags. Suitable for multi-feature CLIs.

```go
package main

import (
  "os"
  "strings"
  "gopkg.in/alecthomas/kingpin.v2"
)

var (
  app      = kingpin.New("chat", "A command-line chat application.")
  debug    = app.Flag("debug", "Enable debug mode.").Bool()
  serverIP = app.Flag("server", "Server address.").Default("127.0.0.1").IP()

  register     = app.Command("register", "Register a new user.")
  registerNick = register.Arg("nick", "Nickname for user.").Required().String()
  registerName = register.Arg("name", "Name of user.").Required().String()

  post        = app.Command("post", "Post a message to a channel.")
  postImage   = post.Flag("image", "Image to post.").File()
  postChannel = post.Arg("channel", "Channel to post to.").Required().String()
  postText    = post.Arg("text", "Text to post.").Strings()
)

func main() {
  switch kingpin.MustParse(app.Parse(os.Args[1:])) {
  // Register user
  case register.FullCommand():
    println(*registerNick)

  // Post message
  case post.FullCommand():
    if *postImage != nil {
    }
    text := strings.Join(*postText, " ")
    println("Post:", text)
  }
}
```

--------------------------------

### Using Custom IP Address List Argument

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Demonstrates how to use the custom IPList function to define an argument that accepts a list of IP addresses.

```go
ips := IPList(kingpin.Arg("ips", "IP addresses to ping."))
```

--------------------------------

### Provide Static Options for Flag Completion

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Uses HintOptions to provide a predefined list of static options for a flag, allowing users to choose from these or provide their own.

```go
app := kingpin.New("completion", "My application with bash completion.")
app.Flag("port", "Provide a port to connect to").
    Required().
    HintOptions("80", "443", "8080").
    IntVar(&c.port)
```

--------------------------------

### Using Custom HTTP Header Flag

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Demonstrates how to use the custom HTTPHeader function to define a flag for adding HTTP headers.

```go
headers = HTTPHeader(kingpin.Flag("header", "Add a HTTP header to the request.").Short('H'))
```

--------------------------------

### Sub-command Definition and Parsing

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Shows how to define nested sub-commands with their own flags and arguments, and how to parse them in the main function. Essential for structured CLIs.

```go
var (
  deleteCommand     = kingpin.Command("delete", "Delete an object.")
  deleteUserCommand = deleteCommand.Command("user", "Delete a user.")
  deleteUserUIDFlag = deleteUserCommand.Flag("uid", "Delete user by UID rather than username.")
  deleteUserUsername = deleteUserCommand.Arg("username", "Username to delete.")
  deletePostCommand = deleteCommand.Command("post", "Delete a post.")
)

func main() {
  switch kingpin.Parse() {
  case "delete user":
  case "delete post":
  }
}
```

--------------------------------

### Set Short Help Flag

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Configures the command-line application to use '-h' as a short flag for displaying help information.

```go
kingpin.CommandLine.HelpFlag.Short('h')
```

--------------------------------

### Provide Dynamic Options for Flag Completion

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Uses HintAction with a function to dynamically generate completion options for a flag, useful for reading from files or databases.

```go
func listHosts() []string {
  // Provide a dynamic list of hosts from a hosts file or otherwise
  // for bash completion. In this example we simply return static slice.

  // You could use this functionality to reach into a hosts file to provide
  // completion for a list of known hosts.
  return []string{"sshhost.example", "webhost.example", "ftphost.example"}
}

app := kingpin.New("completion", "My application with bash completion.")
app.Flag("flag-1", "").HintAction(listHosts).String()
```

--------------------------------

### Run Tests and Generate Coverage Report

Source: https://github.com/baidubce/bce-cmd/blob/master/README.md

Executes tests for specified files or directories and generates an HTML coverage report. Replace $1 with the target file or directory.

```shell
go test -v $1 -coverprofile=c.out
go tool cover -html=c.out -o cover.html
```

--------------------------------

### Convenience Function for HTTP Header Parser

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Provides a convenience function to create and set an HTTP header parser, simplifying its usage with Kingpin flags.

```go
func HTTPHeader(s Settings) (target *http.Header) {
  target = &http.Header{}
  s.SetValue((*HTTPHeaderValue)(target))
  return
}
```

--------------------------------

### Convenience Function for IP Address List Parser

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Provides a convenience function to create and set an IP address list parser, simplifying its usage with Kingpin arguments.

```go
func IPList(s Settings) (target *[]net.IP) {
  target = new([]net.IP)
  s.SetValue((*ipList)(target))
  return
}
```

--------------------------------

### Custom IP Address List Parser

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Implements a custom parser for accumulating a list of IP addresses, conforming to Go's flag.Value interface and supporting cumulative values.

```go
type ipList []net.IP

func (i *ipList) Set(value string) error {
  if ip := net.ParseIP(value); ip == nil {
    return fmt.Errorf("'%s' is not an IP address", value)
  } else {
    *i = append(*i, ip)
    return nil
  }
}

func (i *ipList) String() string {
  return ""
}

func (i *ipList) IsCumulative() bool {
  return true
}
```

--------------------------------

### Custom HTTP Header Parser

Source: https://github.com/baidubce/bce-cmd/blob/master/src/vendor/github.com/alecthomas/kingpin/README.md

Defines a custom parser for accumulating HTTP header values, conforming to Go's flag.Value interface. It splits the input string into a header name and value.

```go
type HTTPHeaderValue http.Header

func (h *HTTPHeaderValue) Set(value string) error {
  parts := strings.SplitN(value, ":", 2)
  if len(parts) != 2 {
    return fmt.Errorf("expected HEADER:VALUE got '%s'", value)
  }
  (*http.Header)(h).Add(parts[0], parts[1])
  return nil
}

func (h *HTTPHeaderValue) String() string {
  return ""
}
```

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