Anatomy of a simple Linux utility
How ls Works
© racorn, 123RF
A simple Linux utility program such as ls might look simple, but many steps happen behind the scenes from the time you type "ls" to the time you see the directory listing. In this article, we look at these behind-the-scene details.
What really happens when you enter a program's name in a terminal window? This article is a journey into the workings of a commonly used program – the ubiquitous ls file listing command. This journey starts with the Bash [1] shell finding the ls program in response to the letters ls typed at the terminal, and it leads to a list of files and directories retrieved from the underlying filesystem [2].
To recreate these results, you'll need some basic understanding of standard debugging techniques using the GNU debugger (gdb), some familiarity with the SystemTap system information utility [3] [4], and an intermediate-level understanding of C programming code. SystemTap is a scripting language and an instrumentation framework that allows you to examine a Linux kernel dynamically. If you don't have all these skills, following along will still give you some insight into the inner workings of a program on Linux.
This article assumes you are running Linux kernel 3.18 [5] with the debug symbols for Bash installed, that a local copy of the 3.18 kernel source is available, and that SystemTap is set up properly. In the next section, I will describe how to configure your system to follow this article.
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Digital Autonomy
• How the Fediverse Found Parts for Its Platforms
• The Answer Was Already on the Shelf
• Changing the Chip Industry: How Public Investment Has Grown Open Silicon
• United Nations Open Source Portal Goes Live
• EU Open Source Strategy Plays Key Role in Tech Sovereignty Package
• France Says “Au Revoir” to Microsoft
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
Linux 7.4 is "Much Healthier" Thanks to AI
At nearly 42 million lines, Linux 7.4 is the largest merge in the history of the kernel.
-
Working Exploit for a Linux Kernel Flaw Made Public
Even before a bug received its CVE identifier or an upstream fix, the local privilege escalation vulnerability exploit found its way into the wild.
-
r/opensource Bans AI-Assisted and AI-Related Projects
The de facto subreddit for all things open source has not only banned AI-related projects but also users who "don't speak English."
-
Bottlenecks Discovered by Meta Engineers Lead to Scalability Improvements
Thanks to a small group of engineers at Meta, the Linux kernel module kernfs has been improved, which has led to some serious gains.
-
PwnEscape Poses VM Vulnerability
A guest-to-host escape flaw in Linux KVM, named PwnEscape, might be yet another means of attacking Linux.
-
Linux Mint 27 Set for a Christmas Release
The developers behind Linux Mint have announced a Christmas release, and it looks like Santa's sack will be brimming with features.
-
Is Linus Torvalds Vibe Coding?
The creator of Linux has added AI into his process for Linux kernel development, and it's more than just for debugging.
-
openKylin 3.0 Released with Expanded AI Integration
The latest release features a pre-installed AI agent to help perform tasks.
-
DigitalOcean Ends Open Source Credits Program
In a change that has surprised many open source developers, DigitalOcean has decided to sunset its Open Source Credits Program.
-
Office 365 Available for Testing on Linux via Bottles
Linux users can now test the official Office 365, thanks to Mirko Brombin's work on Bottles.