Command Line Polling

By  on  

In an ideal world, we wouldn't have to poll for anything; we would always have events to trigger other functions.  This isn't an ideal world, however, so it's important to know how to poll in multiple programming languages.  I've covered JavaScript polling (with and without Promises), but what about command line polling?  For example, ensuring MYSQL is up before attempting to perform more operations.

Here's the basic syntax:

# while ! (command here); do
while ! mysql -uroot; do
  sleep 1
done

The example above performs the mysql -uroot operation (which will fail until mysqld is up) every second.  Keep in mind the poll operation you run should be as simple as possible, just enough to know that what you want to use is available!

Recent Features

  • By
    Create a CSS Flipping Animation

    CSS animations are a lot of fun; the beauty of them is that through many simple properties, you can create anything from an elegant fade in to a WTF-Pixar-would-be-proud effect. One CSS effect somewhere in between is the CSS flip effect, whereby there's...

  • By
    JavaScript Promise API

    While synchronous code is easier to follow and debug, async is generally better for performance and flexibility. Why "hold up the show" when you can trigger numerous requests at once and then handle them when each is ready?  Promises are becoming a big part of the JavaScript world...

Incredible Demos

  • By
    Introducing MooTools LazyLoad

    Once concept I'm very fond of is lazy loading. Lazy loading defers the loading of resources (usually images) until they are needed. Why load stuff you never need if you can prevent it, right? I've created LazyLoad, a customizable MooTools plugin that...

  • By
    Advanced CSS Printing – Using JavaScript Double-Click To Remove Unwanted DIVs

    Like any good programmer, I'm constantly searching around the internet for ideas and articles that can help me improve my code. There are thousands of talented programmers out there so I stumble upon some great articles and code snippets that I like to print out...

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!