利用cli.go来写命令行应用

定义命令和子命令

下面是一个例子:

package mainimport ("fmt""os""github.com/codegangsta/cli"
)func main() {app := cli.NewApp()app.Name = "jasperapp"app.Usage = "sample command-line app by jasper"app.Author = "Carter"app.Email = "jasper@xxx.com"app.Commands = []cli.Command{{Name:      "read",ShortName: "r",Usage:     "read something",Subcommands: []cli.Command{{Name:   "articles",Usage:  "read articles",Action: readArticles,},{Name:   "tweets",Usage:  "read Tweets",Action: readTweets,},},},}app.Run(os.Args)
}func readArticles(ctx *cli.Context) {fmt.Println("Go to http://www.opscoder.info to read articles!")
}func readTweets(ctx *cli.Context) {fmt.Println("Go to http://www.opscoder.info to read our tweets!")
}

如果你不带参数去运行，你将会得到下面的帮助信息：

NAME:jasperapp - sample command-line app by jasperUSAGE:jasperapp [global options] command [command options] [arguments...]VERSION:0.0.0AUTHOR:Carter - <jasper@xxx.com>COMMANDS:read, r  read somethinghelp, h  Shows a list of commands or help for one commandGLOBAL OPTIONS:--help, -h       show help--version, -v    print the version

我们定义一个read子命令，它有articles和tweet两个命令：

jasperapp read articles

输出为：

Go to http://www.opscoder.info to read articles!

或是运行：

jasperapp read tweets

输出为：

Go to http://www.opscoder.info to read our tweets!

使用context

每个动作都有一个context，在下面的例子中函数readArticles和readTweets接收一个参数，我们可以这样使用：

func readArticles(ctx *cli.Context) {fmt.Printf("The first argument was: %s", ctx.Args().First())
}

现在运行jasperapp read articles please将会输出：

The first argument was: please

使用flags

为了展示flags的用法，我们稍微修改一下tweets子命令：

{Name:   "tweets",Usage:  "read Tweets",Flags: []cli.Flag{cli.StringFlag{Name: "account",Value: "TheJasper",Usage: "name of Twitter account",},},Action: readTwitter,
},

其中readTweets函数这么写：

func readTwitter(ctx *cli.Context) {fmt.Printf("Go to http://www.opscoder.info/%s to read tweets!", ctx.String("account"))
}

现在让我们编译结果并查看下tweets子命令的帮助信息:

jasperapp read tweets --help

输出如下：

NAME:tweets - read TweetsUSAGE:command tweets [command options] [arguments...]OPTIONS:--account 'TheJasper' name of Twitter account

现在让我们试试：

$ jasperapp read tweets
Go to  http://www.opscoder.info/TheJasper to read tweets!$ jasperapp read tweets --account codegangsta
Go to  http://www.opscoder.info/codegangsta to read tweets!

总结

Cli.go还有很多自定义的东西，具体可以参考Godoc的文档。