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
    From Webcam to Animated GIF: the Secret Behind chat.meatspac.es!

    My team mate Edna Piranha is not only an awesome hacker; she's also a fantastic philosopher! Communication and online interactions is a subject that has kept her mind busy for a long time, and it has also resulted in a bunch of interesting experimental projects...

  • By
    7 Essential JavaScript Functions

    I remember the early days of JavaScript where you needed a simple function for just about everything because the browser vendors implemented features differently, and not just edge features, basic features, like addEventListener and attachEvent.  Times have changed but there are still a few functions each developer should...

Incredible Demos

  • By
    MooTools PulseFade Plugin

    I was recently driven to create a MooTools plugin that would take an element and fade it to a min from a max for a given number of times. Here's the result of my Moo-foolery. The MooTools JavaScript Options of the class include: min: (defaults to .5) the...

  • By
    jQuery Wookmark

    The first thing that hits you when you visit Pinterest is "Whoa, the columns are the same width and the photos are cut to fit just the way they should."  Basic web users probably think nothing of it but as a developer, I can appreciate the...

Discussion

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