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

Incredible Demos

  • By
    Custom Scrollbars in WebKit

    Before each of the browser vendors we like was providing unique CSS controls, Internet Explorer was setting the tone.  One such example is IE's early implementation of CSS filters. Internet Explorer was also the first browser that allowed developers to, for better or worse, customize...

  • By
    dat.gui:  Exceptional JavaScript Interface Controller

    We all love trusted JavaScript frameworks like MooTools, jQuery, and Dojo, but there's a big push toward using focused micro-frameworks for smaller purposes. Of course, there are positives and negatives to using them.  Positives include smaller JS footprint (especially good for mobile) and less cruft, negatives...

Discussion

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