Book Excerpt: Linux Programming by Example, Part 2
The V7 ls is a relatively small program, yet it touches on many of the fundamental aspects of Unix programming: file I/O, file metadata, directory contents, users and groups, time and date values, sorting and dynamic memory management.
The most notable external difference between V7 ls and modern ls is the treatment of the -a and -l options. The V7 version has many fewer options than do modern versions; a noticeable lack is the -R recursive option.
The management of flist is a clean way to use the limited memory of the PDP-11 architecture yet still provide as much information as possible. The struct lbuf nicely abstracts the information of interest from the struct stat; this simplifies the code considerably. The code for printing the nine permission bits is compact and elegant.
Some parts of ls use surprisingly small limits, such as the upper bound of 1024 on the number of files or the buffer size of 100 in makename().
Arnold Robbins is a professional programmer and technical author. He is the long-time maintainer of gawk, the GNU Project's version of the Awk programming language. He is the author of numerous well-known technical books, such as Linux Programming by Example: The Fundamentals, recently published by Prentice Hall, as well as Unix In A Nutshell, Learning the vi Editor and Effective awk Programming, published by O'Reilly Media Inc. He is happily married with four wonderful children. Arnold is an amateur Talmudist and particularly enjoys studying the Jerusalem Talmud. He can be reached at firstname.lastname@example.org.
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
|Fancy Tricks for Changing Numeric Base||May 29, 2016|
|Working with Command Arguments||May 28, 2016|
|Secure Desktops with Qubes: Installation||May 28, 2016|
|CentOS 6.8 Released||May 27, 2016|
|Secure Desktops with Qubes: Introduction||May 27, 2016|
|Chris Birchall's Re-Engineering Legacy Software (Manning Publications)||May 26, 2016|
- Tips for Optimizing Linux Memory Usage
- Secure Desktops with Qubes: Introduction
- Working with Command Arguments
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- Secure Desktops with Qubes: Installation
- Fancy Tricks for Changing Numeric Base
- CentOS 6.8 Released
- Linux Mint 18
- The Italian Army Switches to LibreOffice
- Petros Koutoupis' RapidDisk
Until recently, IBM’s Power Platform was looked upon as being the system that hosted IBM’s flavor of UNIX and proprietary operating system called IBM i. These servers often are found in medium-size businesses running ERP, CRM and financials for on-premise customers. By enabling the Power platform to run the Linux OS, IBM now has positioned Power to be the platform of choice for those already running Linux that are facing scalability issues, especially customers looking at analytics, big data or cloud computing.
￼Running Linux on IBM’s Power hardware offers some obvious benefits, including improved processing speed and memory bandwidth, inherent security, and simpler deployment and management. But if you look beyond the impressive architecture, you’ll also find an open ecosystem that has given rise to a strong, innovative community, as well as an inventory of system and network management applications that really help leverage the benefits offered by running Linux on Power.Get the Guide