Driving One's Own Audio Device
The device driver interface offers other device methods in addition to the open/close and read/write pairs. While none of them is critical to device operation, I usually add a few lines of code to implement select and lseek. The former is needed by those programs which multiplex several input/output channels or use non-blocking operations to read and write data. Its role is quite needed if you run real programs, and the implementation is straightforward enough that I won't show it here. The implementation of lseek, on the other hand, consists of the one line return -ESPIPE; and is meant to tell any program that tries to lseek the device that this “is a pipe” (reported to user space as “Illegal seek”).
My aversion to computer sound makes me a novice in the field, and I really don't know anything about programs that play audio, or sites where audio files can be retrieved. Although Linus Torvalds offered an interesting “I pronounce Linux as Linux”, the file was not enough to test my device, and I needed to generate some audio data. The result is the sad distribution includes a program that plays sinusoidal waves, one that plays square waves and a not-so-good piano implementation. These tools work with any /dev/audio you happen to run and can be fun to play with, especially if you have a scope near your Linux box.
All code for the sad program is available by anonymous download in the file ftp.linuxjournal.com/pub/lj/listings/issue53/2997.tgz.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.View Now!
|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- The Firebird Project's Firebird Relational Database
- Stunnel Security for Oracle
- My +1 Sword of Productivity
- Managing Linux Using Puppet
- Non-Linux FOSS: Caffeine!
- SUSE LLC's SUSE Manager
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Parsing an RSS News Feed with a Bash Script
- Google's SwiftShader Released
- Doing for User Space What We Did for Kernel Space
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide