command.go

package main

import (
	"flag"
	"fmt"
	"os"
	"strings"
	"sync"
)

// Command is an implementation of a subcommand
// like mongotool dump or mongotool restore.
// This structure is stolen from how the main go tools is defined: http://golang.org/src/cmd/go/main.go
type Command struct {
	// Run runs the command.
	// The args are the arguments after the command name.
	Run func(cmd *Command, args []string)

	// UsageLine is the one-line usage message.
	// The first word in the line is taken to be the command name.
	UsageLine string

	// Short is the short description shown in the 'go help' output.
	Short string

	// Long is the long message shown in the 'go help <this-command>' output.
	Long string

	// Flag is a set of flags specific to this command.
	Flag flag.FlagSet

	// CustomFlags indicates that the command will do its own
	// flag parsing.
	CustomFlags bool
}

// Name returns the command's name: the first word in the usage line.
func (c *Command) Name() string {
	name := c.UsageLine
	i := strings.Index(name, " ")
	if i >= 0 {
		name = name[:i]
	}
	return name
}

func (c *Command) Usage() {
	fmt.Fprintf(os.Stderr, "usage: %s\n\n", c.UsageLine)
	fmt.Fprintf(os.Stderr, "%s\n", strings.TrimSpace(c.Long))
	os.Exit(2)
}

var exitStatus = 0
var exitMu sync.Mutex

func setExitStatus(n int) {
	exitMu.Lock()
	if exitStatus < n {
		exitStatus = n
	}
	exitMu.Unlock()
}

var atexitFuncs []func()

func atexit(f func()) {
	atexitFuncs = append(atexitFuncs, f)
}

func exit() {
	for _, f := range atexitFuncs {
		f()
	}
	os.Exit(exitStatus)
}

func errorf(format string, args ...interface{}) {
	fmt.Printf(format, args...)
	fmt.Println()
	setExitStatus(1)
}