Go - Flag (Argument Parsing)

Change the usage (adding an header, footer)

To change the usage output, you need to overwrite the Usage variable.

Example to add an header and a footer

flag.Usage = func() {
	fmt.Fprintln(os.Stderr, "An header")
	fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
	flag.PrintDefaults()
	fmt.Fprintln(os.Stderr, "A footer")
}

Get the arguments without flag (the last arguments)

The non-flag arguments are available from flag.Args()

fmt.Println("tail:", flag.Args())