Notes - Cobra Commander for Go

Creating a CLI program by using Cobra Generator

This is a step by step on how to create a Go program to generate a liquidation report by using Cobra Generator.

First, get the Cobra Generator

1
go get github.com/spf13/cobra/cobra

Using the Cobra Generator to create the structure for our program

1
2
mkdir -p rl && cd rl
cobra init --pkg-name rl

How to add sub-commands?

Create a report subcommand

1
cobra add report

Note: Although rl liquidation are concise, I prefer to use rl report liquidation for this convey information more accurately. Later on I can have rl report concession, rl report sn, etc.

Create a liquidation subcommand for report so that you can use rl report liquidation to generate the liquidation report.

1
2
3
4
// -p, --parent string   variable name of parent command for this command (default "rootCmd")
// Note: using the variable name of parent command(reportCmd in this case)
// You can find the report command variable name in the rl/cmd/report.go
cobra add liquidation -p reportCmd

Create a liquidation sub-folder in rl and doing the report generating job in rl/liquidation/main.go

1
2
3
4
5
6
7
// 1. in it's own package(not package main)
package liquidation
import ...

// 2. export Main
func Main(){...}
...

Update Cobra command file rl/cmd/liquidation.go

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
package cmd

import (
    // 1. import the liquidation package
    "github.com/AngangGuo/rl/liquidation"
    "github.com/spf13/cobra"
)

// liquidationCmd represents the liquidation command
var liquidationCmd = &cobra.Command{
    Use:   "liquidation",
    Short: "Create the Weekly RL Liquidation Report",
    Long: `Create the Weekly RL Liquidation Report from Inventory All Fields file.

1. Download the latest Inventory All Filelds CSV file from Egnyte. 
2. Create the Weekly RL Liquidation Report from this CSV file.

Usage:
rl report liquidation: Create Weekly RL Liquidation Report

Options:
rl report liquidation --download=false (-d=false): Skip downloading Inventory All Fields CSV file
rl report liquidation --amazon (-a): RL Liquidation Report and Amazon Liquidation Report     
     
`,
	
    // 2. hook the liquidation function here
    Run: func(cmd *cobra.Command, args []string) {
        liquidation.Main()
    },
}

func init() {
    // Cobra added these automatically when running command `cobra add liquidation -p reportCmd`
    reportCmd.AddCommand(liquidationCmd)
}	

Add rl report liquidation and other commands in the same way as above

How to add local flags?

Add flags: to add download and amazon flags in cmd/liquidation.go:

1
2
3
4
5
6
7
func init() {
	reportCmd.AddCommand(liquidationCmd)

    // 1. Add local flags to liquidation subcommand
	liquidationCmd.Flags().BoolP("download", "d", true, "Download Inventory All Fields CSV file")
	liquidationCmd.Flags().BoolP("amazon", "a", false, "Create Weekly Amazon Liquidation Report")
}

Get flag value:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
...
	Run: func(cmd *cobra.Command, args []string) {
	    // 2. Get local flags' value
		download,err:=cmd.Flags().GetBool("download")
		if err != nil {
			log.Fatalln(err)
		}
		amazon,err:=cmd.Flags().GetBool("amazon")
		if err != nil {
			log.Fatalln(err)
		}
		
		option := liquidation.Option{
			Download: download,
			Amazon:   amazon,
		}
		
		liquidation.Main(option)
	},
}

You can define your own variable and use it as flag value receiver:

1
2
3
4
5
var download = false
...
liquidationCmd.Flags().BoolVarP(&download, "download", "d", true, "Download Inventory All Fields CSV file")

// Use the "download" variable directly anywhere in its scope

Examples

1
2
3
4
5
6
7
8
9
// The "verbose" flag is persistent and global. 
// Which means you can tell the program to show you details of the program execution with any command and flag set.
rootCmd.PersistentFlags().BoolVarP(&verbose, "verbose", "v", false, "Verbose output")

myCmd.Flags().IntVarP(&countFlag, "count", "c", 0, "A count of random numbers")
// Must provide the "count" flag
myCmd.MarkFlagRequired("count")

myCmd.Flags().StringSliceVarP(&rangeFlag, "range", "r" []string{"1:100"}, "Range of numbers. Optional")

Help

rl --help
rl report --help
rl report liquidation --help

Command Completion

You can generate the autocompletion script for Bash/Fish/PowerShell/Zsh.

Generate PowerShell completion script by using:

rl completion powershell