laravel 5.2 How to get route parameter in blade?

In Laravel 8, you can simply use request()->route('parameter_name').

If you want to get the parameters without using the controller method

{{dd(request()->route()->parameters)}}

I'm not sure what you mean. If you're trying to construct the route in a Blade template, use

<a href="{{ route('blog.by.slug', ['slug' => 'someslug']) }}">...</a>

If you're trying to access the given parameter, I would suggest passing it from the controller:

// CmsController
public function show($slug)
{
    // other stuff here
    return view('someview', compact('slug'));
}

// someview.blade.php
{{ $slug }}

And if you really need to access the parameter from the view without first sending it from the controller... you really shouldn't, but you can use the facade:

{{ Request::route('slug') }}