Shell test conditions and exit codes
Tutorials – Shell Scripting
The Bash shell uses different criteria to make decisions. Learn how to teach your shell scripts to make the right choice.
In the previous installment of this series [1], I described how to add different possible courses of action to a script, so that the script can choose by itself which action to execute while running. In this issue, I will explain how to teach a script to choose which of the available actions to execute.
Often, the real decision-making challenge lies not in figuring out whether your shell script needs a while loop or some nested if statements but rather in determining the conditions that will tell your script when it should stop that loop or which branch of that "if" statement to execute. The main Bash tools for this purpose are a big set of test operators (see the descriptions online [2] [3] [4]) and their corresponding syntax, which can evaluate whether some condition is true or false. By contrast, exit status codes [5] are the traces that built-in commands, or whole scripts, leave behind to communicate their achievements.
In this article you will learn through examples and working code:
[...]
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
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
-
KDE Sets Ambitious Goals for 2026 and Beyond
KDE Connect reveals the goals for the Linux desktop darling, with one of those goals long overdue.
-
It’s Time to Test Fedora 45 Beta
Fedora 45 beta has been released with updated Gnome, KDE Plasma, and kernel.
-
Ubuntu Stonking Stingray Gets Even Rustier
Ubuntu 26.10 has completed its migration to the Rust-based coreutils.
-
AI Fixes Linux Bottlenecks Using “Hideous” Code
A Linux developer used AI to fix bottlenecks that caused problems when building the kernel. The resulting AI-generated code needed a lot of work.
-
Advanced Video Coding Still Under Patent
Brazilian patent BRPI0109962B1 has expired, which means that DivX and Xvid are no longer problematic for Linux, but it doesn’t mean that video is all of a sudden fully unleashed.
-
2,000 Vulnerabilities per Linux Release
Thanks to AI bug hunters, the Linux kernel is seeing record numbers of vulnerabilities, and it's overwhelming developers.
-
Linux Exempt from California’s Age Verification Law
So long as Linux is distributed under the GPL, MIT, BSD, and Apache licenses, the OS is exempt from being required to verify the age of its users in California.
-
Roll Out the Cake: Linux Turns 35
35 years ago, a Finnish student began a humble project that would forever change the course of technology.
-
China Switching from Windows to Linux
China has ordered several government agencies to drop a Chinese-developed version of Windows 10 in favor of either KylinOS or UOS.
-
Pine64 Halts Production of Linux Devices
With continued DRAM and eMMC shortages, Pine64 has decided to discontinue production of Linux devices.