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
    Facebook Open Graph META Tags

    It's no secret that Facebook has become a major traffic driver for all types of websites.  Nowadays even large corporations steer consumers toward their Facebook pages instead of the corporate websites directly.  And of course there are Facebook "Like" and "Recommend" widgets on every website.  One...

  • By
    Welcome to My New Office

    My first professional web development was at a small print shop where I sat in a windowless cubical all day. I suffered that boxed in environment for almost five years before I was able to find a remote job where I worked from home. The first...

Incredible Demos

  • By
    Create a Simple News Scroller Using MooTools, Part I:  The Basics

    News scroller have been around forever on the internet. Why? Because they're usually classy and effective. Over the next few weeks, we'll be taking a simple scroller and making it into a flexible, portable class. We have to crawl before we...

  • By
    Create a Dynamic Flickr Image Search with the Dojo Toolkit

    The Dojo Toolkit is a treasure chest of great JavaScript classes.  You can find basic JavaScript functionality classes for AJAX, node manipulation, animations, and the like within Dojo.  You can find elegant, functional UI widgets like DropDown Menus, tabbed interfaces, and form element replacements within...

Discussion

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