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
    6 Things You Didn’t Know About Firefox OS

    Firefox OS is all over the tech news and for good reason:  Mozilla's finally given web developers the platform that they need to create apps the way they've been creating them for years -- with CSS, HTML, and JavaScript.  Firefox OS has been rapidly improving...

  • By
    Responsive and Infinitely Scalable JS Animations

    Back in late 2012 it was not easy to find open source projects using requestAnimationFrame() - this is the hook that allows Javascript code to synchronize with a web browser's native paint loop. Animations using this method can run at 60 fps and deliver fantastic...

Incredible Demos

Discussion

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