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
US / Canada
UK / Australia
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
-
Plasma Bigscreen Returns
A developer discovered that the Plasma Bigscreen feature had been sitting untouched, so he decided to do something about it.
-
CachyOS Now Lets Users Choose Their Shell
Imagine getting the opportunity to select which shell you want during the installation of your favorite Linux distribution. That's now a thing.
-
Wayland 1.24 Released with Fixes and New Features
Wayland continues to move forward, while X11 slowly vanishes into the shadows, and the latest release includes plenty of improvements.
-
Bugs Found in sudo
Two critical flaws allow users to gain access to root privileges.
-
Fedora Continues 32-Bit Support
In a move that should come as a relief to some portions of the Linux community, Fedora will continue supporting 32-bit architecture.
-
Linux Kernel 6.17 Drops bcachefs
After a clash over some late fixes and disagreements between bcachefs's lead developer and Linus Torvalds, bachefs is out.
-
ONLYOFFICE v9 Embraces AI
Like nearly all office suites on the market (except LibreOffice), ONLYOFFICE has decided to go the AI route.
-
Two Local Privilege Escalation Flaws Discovered in Linux
Qualys researchers have discovered two local privilege escalation vulnerabilities that allow hackers to gain root privileges on major Linux distributions.
-
New TUXEDO InfinityBook Pro Powered by AMD Ryzen AI 300
The TUXEDO InfinityBook Pro 14 Gen10 offers serious power that is ready for your business, development, or entertainment needs.
-
LibreOffice Tested as Possible Office 365 Alternative
Another major organization has decided to test the possibility of migrating from Microsoft's Office 365 to LibreOffice.