func (*Group) lookUp(line string, f field, value interface{}) interface{} {
	_field := f.(groupField)
	allField := strings.Split(line, ":")
	arrayField := make(map[int][]string)
	intField := make(map[int]int)

	arrayField[3] = strings.Split(allField[3], ",")

	// Check integers
	var err error
	if intField[2], err = strconv.Atoi(allField[2]); err != nil {
		panic(atoiError{_GROUP_FILE, line, "GID"})
	}

	// Check fields
	var isField bool
	if G_NAME&_field != 0 && allField[0] == value.(string) {
		isField = true
	} else if G_PASSWD&_field != 0 && allField[1] == value.(string) {
		isField = true
	} else if G_GID&_field != 0 && intField[2] == value.(int) {
		isField = true
	} else if G_MEMBER&_field != 0 && checkGroup(arrayField[3], value.(string)) {
		isField = true
	} else if G_ALL&_field != 0 {
		isField = true
	}

	if isField {
		return &Group{
			Name:     allField[0],
			password: allField[1],
			GID:      intField[2],
			UserList: arrayField[3],
		}
	}
	return nil
}
func (*Group) lookUp(line string, f field, value interface{}) interface{} {
	_field := f.(groupField)
	allField := strings.Split(line, ":")
	arrayField := make(map[int][]string)
	intField := make(map[int]int)

	arrayField[3] = strings.Split(allField[3], ",")

	// Check integers
	var err error
	if intField[2], err = strconv.Atoi(allField[2]); err != nil {
		panic(atoiError{_GROUP_FILE, line, "GID"})
	}

	// Check fields
	var isField bool
	if G_NAME&_field != 0 && allField[0] == value.(string) {
		isField = true
	} else if G_PASSWD&_field != 0 && allField[1] == value.(string) {
		isField = true
	} else if G_GID&_field != 0 && intField[2] == value.(int) {
		isField = true
	} else if G_MEMBER&_field != 0 && checkGroup(arrayField[3], value.(string)) {
		isField = true
	} else if G_ALL&_field != 0 {
		isField = true
	}

	if isField {
		return &Group{
			Name:     allField[0],
			password: allField[1],
			GID:      intField[2],
			UserList: arrayField[3],
		}
	}
	return nil
}
// == Lookup
//
// lookUp parses the group line searching a value into the field.
// Returns nil if it is not found.