cobra 库是 golang 的一个开源第三方库,能够快速便捷的建立命令行应用程序。
比如:
ls -a
git add .
gcc a.c -o app
…
这些都是命令,二前面的ls、git、gcc等都是我们写的程序。如果不使用 cobra 框架进行编写这些命令,那么程序写起来是相当费劲的。
cobra由三部分构成:commands,arguments 和 flags:
commands:表示要执行的动作。每一个 command 表示应用程序的一个动作。每个命令可以包含子命令。
arguments:给动作传入的参数。
flags:表示动作的行为。可以设置执行动作的行为。flags 包括两种:对某个命令生效和对所有命令生效。
比如:./app echo time helloword -t 4
中,app
就是程序,echo
就是子命令,time
是 echo
的子命令,helloword
是传入的参数,-t
是则是 flags
。
这个例子的目录结构如下:
▾ pro_test/
___▾ cmd/
______echo.go
______print.go
______times.go
______root.go
main.go
package cmd
import "github.com/spf13/cobra"
var rootCmd = &cobra.Command{
Use: "app [command]",
}
func Execute() {
rootCmd.Execute()
}
package cmd
import (
"fmt"
"github.com/spf13/cobra"
"strings"
)
var cmdPrint = &cobra.Command{
Use: "Print [string to print]",
Short: "Print anything to the screen",
Long: `print is for printing anything back to the screen.
For many years people have printed back to the screen.`,
Args: cobra.MinimumNArgs(1),
Run: func(cmd *cobra.Command, args []string) {
fmt.Println("Print: " + strings.Join(args, " "))
},
}
func init() {
rootCmd.AddCommand(cmdPrint)
}
package cmd
import (
"fmt"
"github.com/spf13/cobra"
"strings"
)
var cmdEcho = &cobra.Command{
Use: "echo [string to echo]",
Short: "Echo anything to the screen",
Long: `echo is for echoing anything back.
Echo works a lot like print, except it has a child command.`,
Args: cobra.MinimumNArgs(1),
Run: func(cmd *cobra.Command, args []string) {
fmt.Println("Print: " + strings.Join(args, " "))
},
}
func init() {
rootCmd.AddCommand(cmdEcho)
}
package cmd
import (
"fmt"
"github.com/spf13/cobra"
"strings"
)
var echoTimes int
var cmdTimes = &cobra.Command{
Use: "time [# times] [string to echo]",
Short: "Echo anything to the screen more times",
Long: `echo things multiple times back to the user y providing
a count and a string.`,
Args: cobra.MinimumNArgs(1),
Run: func(cmd *cobra.Command, args []string) {
for i := 0; i < echoTimes; i++ {
fmt.Println("Echo: " + strings.Join(args, " "))
}
},
}
func init() {
cmdTimes.Flags().IntVarP(&echoTimes, "times", "t", 1, "times to echo the input")
cmdEcho.AddCommand(cmdTimes)
}
main.go的作用就是初始化:
package main
import "projects_20/pro_1_example/cmd"
func main() {
cmd.Execute()
}
键入:go build -o app
,就可以得到一个 名为app 的命令行应用程序。
cobra帮我们生成了很棒的 help 信息:
(base) ***@shenjian pro_1_example % ./app -h
Usage:
app [command]
Available Commands:
Print Print anything to the screen
completion Generate the autocompletion script for the specified shell
echo Echo anything to the screen
help Help about any command
Flags:
-h, --help help for app
Use "app [command] --help" for more information about a command.
可以看到Available Commands有四个命令,试试 echo 这个命令:
(base) ***@shenjian pro_1_example % ./app echo -h
echo is for echoing anything back.
Echo works a lot like print, except it has a child command.
Usage:
app echo [string to echo] [flags]
app echo [command]
Available Commands:
time Echo anything to the screen more times
Flags:
-h, --help help for echo
Use "app echo [command] --help" for more information about a command.
可以看到Usage 选项有两个方法,而且里面还有一个子命令 time。看看 time 是怎么使用的:
(base) luliang@shenjian pro_1_example % ./app echo time -h
echo things multiple times back to the user y providing
a count and a string.
Usage:
app echo time [# times] [string to echo] [flags]
Flags:
-h, --help help for time
-t, --times int times to echo the input (default 1)
这个 Usage 就是用法,试试:
(base) ***@shenjian pro_1_example % ./app echo time helloworld -t 6
Echo: helloworld
Echo: helloworld
Echo: helloworld
Echo: helloworld
Echo: helloworld
Echo: helloworld
可以看到命令正常使用,太棒了!
标志提供修饰符以控制命令的操作方式。由于标志是在不同位置定义和使用的,我们需要在外部定义一个具有正确作用域的变量,以分配要使用的标志。
全局标志:
rootCmd.PersistentFlags().BoolVarP(&verbose, "verbose", "v", false, "verbose output")
局部标志:
localCmd.Flags().StringVarP(&Source, "source", "s", "", "Source directory to read from")
全文完,感谢阅读。