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
    Create Twitter-Style Buttons with the Dojo Toolkit

    I love that JavaScript toolkits make enhancing web pages incredibly easy. Today I'll cover an effect that I've already coded with MooTools: creating a Twitter-style animated "Sign In" button. Check out this five minute tutorial so you can take your static...

  • By
    New MooTools Plugin:  ElementFilter

    My new MooTools plugin, ElementFilter, provides a great way for you to allow users to search through the text of any mix of elements. Simply provide a text input box and ElementFilter does the rest of the work. The XHTML I've used a list for this example...

Discussion

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