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
    Use Custom Missing Image Graphics Using MooTools

    Missing images on your website can make you or your business look completely amateur. Unfortunately sometimes an image gets deleted or corrupted without your knowledge. You'd agree with me that IE's default "red x" icon looks awful, so why not use your own missing image graphic? The MooTools JavaScript Note that...

  • By
    Sliding Labels Using MooTools

    A week back I saw a great effect created by CSSKarma: input labels being animated horizontally. The idea is everything positive: elegant, practical, unobtrusive, and requires very little jQuery code. Luckily the effect doesn't require much MooTools code either! The HTML A...

Discussion

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