utils/flags.go

package utils

import (
	"fmt"
	"os"

	flag "github.com/docker/docker/pkg/mflag"
)

// ParseFlags is a utility function that adds a help flag if withHelp is true,
// calls cmd.Parse(args) and prints a relevant error message if there are
// incorrect number of arguments. It returns error only if error handling is
// set to ContinueOnError and parsing fails. If error handling is set to
// ExitOnError, it's safe to ignore the return value.
// TODO: move this to a better package than utils
func ParseFlags(cmd *flag.FlagSet, args []string, withHelp bool) error {
	var help *bool
	if withHelp {
		help = cmd.Bool([]string{"#help", "-help"}, false, "Print usage")
	}
	if err := cmd.Parse(args); err != nil {
		return err
	}
	if help != nil && *help {
		cmd.Usage()
		// just in case Usage does not exit
		os.Exit(0)
	}
	if str := cmd.CheckArgs(); str != "" {
		ReportError(cmd, str, withHelp)
	}
	return nil
}

func ReportError(cmd *flag.FlagSet, str string, withHelp bool) {
	if withHelp {
		if os.Args[0] == cmd.Name() {
			str += ". See '" + os.Args[0] + " --help'"
		} else {
			str += ". See '" + os.Args[0] + " " + cmd.Name() + " --help'"
		}
	}
	fmt.Fprintf(cmd.Out(), "docker: %s.\n", str)
	os.Exit(1)
}