framework/console/controllers/HelpController.php
public function actionUsage($action)
    {
        $result = Yii::$app->createController($action);

        if ($result === false || !($result[0] instanceof Controller)) {
            return;
        }

        /** @var Controller $controller */
        list($controller, $actionID) = $result;
        $action = $controller->createAction($actionID);
        if ($action === null) {
            return;
        }

        $scriptName = $this->getScriptName();
        if ($action->id === $controller->defaultAction) {
            $this->stdout($scriptName . ' ' . $this->ansiFormat($controller->getUniqueId(), Console::FG_YELLOW));
        } else {
            $this->stdout($scriptName . ' ' . $this->ansiFormat($action->getUniqueId(), Console::FG_YELLOW));
        }

        foreach ($controller->getActionArgsHelp($action) as $name => $arg) {
            if ($arg['required']) {
                $this->stdout(' <' . $name . '>', Console::FG_CYAN);
            } else {
                $this->stdout(' [' . $name . ']', Console::FG_CYAN);
            }
        }

        $this->stdout("\n");
    }
public function actionUsage($action)
    {
        $result = Yii::$app->createController($action);

        if ($result === false || !($result[0] instanceof Controller)) {
            return;
        }

        /** @var Controller $controller */
        list($controller, $actionID) = $result;
        $action = $controller->createAction($actionID);
        if ($action === null) {
            return;
        }

        $scriptName = $this->getScriptName();
        if ($action->id === $controller->defaultAction) {
            $this->stdout($scriptName . ' ' . $this->ansiFormat($controller->getUniqueId(), Console::FG_YELLOW));
        } else {
            $this->stdout($scriptName . ' ' . $this->ansiFormat($action->getUniqueId(), Console::FG_YELLOW));
        }

        foreach ($controller->getActionArgsHelp($action) as $name => $arg) {
            if ($arg['required']) {
                $this->stdout(' <' . $name . '>', Console::FG_CYAN);
            } else {
                $this->stdout(' [' . $name . ']', Console::FG_CYAN);
            }
        }

        $this->stdout("\n");
    }
Displays usage information for $action.

@param string $action route to action
@since 2.0.11