Cobra for Real CLIs

Cobra is what kubectl, docker, gh, helm, and hugo use. It's the de facto standard for Go CLIs.

go get github.com/spf13/cobra@latest

Project Structure

mytool/
├── cmd/
│   ├── root.go      # root command, global flags
│   ├── lint.go       # mytool lint
│   └── validate.go   # mytool validate
├── main.go           # just calls cmd.Execute()
└── go.mod

Root Command

// cmd/root.go
package cmd

import (
    "fmt"
    "os"
    "github.com/spf13/cobra"
)

var cfgFile string

var rootCmd = &cobra.Command{
    Use:   "mytool",
    Short: "Infrastructure config toolkit",
    Long:  "Validate, lint, and transform infrastructure configuration files.",
}

func Execute() {
    if err := rootCmd.Execute(); err != nil {
        fmt.Fprintln(os.Stderr, err)
        os.Exit(1)
    }
}

func init() {
    rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file path")
}

Subcommands

// cmd/lint.go
package cmd

import (
    "fmt"
    "github.com/spf13/cobra"
)

var strict bool

var lintCmd = &cobra.Command{
    Use:   "lint [files...]",
    Short: "Lint config files for common issues",
    Args:  cobra.MinimumNArgs(1),
    RunE: func(cmd *cobra.Command, args []string) error {
        for _, file := range args {
            if err := lintFile(file); err != nil {
                return fmt.Errorf("linting %s: %w", file, err)
            }
        }
        return nil
    },
}

func init() {
    lintCmd.Flags().BoolVar(&strict, "strict", false, "treat warnings as errors")
    rootCmd.AddCommand(lintCmd)
}

var validateCmd = &cobra.Command{
    Use:   "validate [files...]",
    Short: "Validate config files against the schema",
    Args:  cobra.,
    : func(cmd *cobra.Command, args []string) error {
        for _, file := range args {
            if err := validateFile(file); err != nil {
                return fmt.Errorf("validating %s: %w", file, err)
            }
        }
        return nil
    },
}

func init() {
    rootCmd.(validateCmd)
}

Key Concepts

# Python: argparse or click
# Go: flag for simple, Cobra for real CLIs
# The patterns are nearly identical — subcommands, flags, validation.
# Cobra just has better shell completion and help generation.