Generated Help Text

The default help flag (-h/--help) is defined as cli.HelpFlag and is checked by the cli internals in order to print generated help text for the app, command, or subcommand, and break execution.

Customization

All of the help text generation may be customized, and at multiple levels. The templates are exposed as variables AppHelpTemplate, CommandHelpTemplate, and SubcommandHelpTemplate which may be reassigned or augmented, and full override is possible by assigning a compatible func to the cli.HelpPrinter variable, e.g.:

package main

import (
    "fmt"
    "io"
    "os"

    "github.com/urfave/cli/v2"
)

func main() {
    // EXAMPLE: Append to an existing template
    cli.AppHelpTemplate = fmt.Sprintf(`%s

WEBSITE: http://awesometown.example.com

SUPPORT: support@awesometown.example.com

`, cli.AppHelpTemplate)

    // EXAMPLE: Override a template
    cli.AppHelpTemplate = `NAME:
   {{.Name}} - {{.Usage}}
USAGE:
   {{.HelpName}} {{if .VisibleFlags}}[global options]{{end}}{{if .Commands}} command [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}
   {{if len .Authors}}
AUTHOR:
   {{range .Authors}}{{ . }}{{end}}
   {{end}}{{if .Commands}}
COMMANDS:
{{range .Commands}}{{if not .HideHelp}}   {{join .Names ", "}}{{ "\t"}}{{.Usage}}{{ "\n" }}{{end}}{{end}}{{end}}{{if .VisibleFlags}}
GLOBAL OPTIONS:
   {{range .VisibleFlags}}{{.}}
   {{end}}{{end}}{{if .Copyright }}
COPYRIGHT:
   {{.Copyright}}
   {{end}}{{if .Version}}
VERSION:
   {{.Version}}
   {{end}}
`

    // EXAMPLE: Replace the `HelpPrinter` func
    cli.HelpPrinter = func(w io.Writer, templ string, data interface{}) {
        fmt.Println("Ha HA.  I pwnd the help!!1")
    }

    (&cli.App{}).Run(os.Args)
}

The default flag may be customized to something other than -h/--help by setting cli.HelpFlag, e.g.:

package main

import (
    "os"

    "github.com/urfave/cli/v2"
)

func main() {
    cli.HelpFlag = &cli.BoolFlag{
        Name:    "haaaaalp",
        Aliases: []string{"halp"},
        Usage:   "HALP",
        EnvVars: []string{"SHOW_HALP", "HALPPLZ"},
    }

    (&cli.App{}).Run(os.Args)
}