Deciphering Dashes: – vs — In Linux command line syntax, the humble dash plays an important role. Both the single dash “-” and double dash “–” are used to specify command options, but they function differently. Understanding when to use each dash type can unlock the full power and flexibility of Linux commands. This article…
The Challenges of Parsing Raw argv Input Command line programs often need to accept input options to customize their behavior. However, directly parsing the raw argv array received by main() can be challenging. The position and order of options may vary, optional arguments may or may not be present, and additional validation code is needed…
The Dangers of Unescaped User Input in Shell Commands Shell commands can be vulnerable to injection attacks if untrusted user input is inserted without proper escaping. Attackers can craft malicious input strings to inject extra commands that get executed by the shell. This can lead to unauthorized access, data loss, denial of service, and other…
The Meaning of the Double Dash The double dash (–) is a special syntax in Linux command line utilities used to signify different behaviors depending on the context. At a basic level, the double dash separates options from arguments in a command. However, its meaning goes deeper than that. The double dash is commonly used…
Ensuring Reliable Input with Bash Read The Bash read command allows input from the user to be assigned to variables for later use in scripts and programs. However, care must be taken to properly validate and sanitize this input before relying on it for critical operations. Why Validate User Input User input from the Bash…
Failing to Properly Quote Variables One of the most common pitfalls when assigning command output to a variable in Bash is failing to properly quote the variable expansion. When you assign output to a variable without quoting, like this: out=$(mycommand) Bash will perform word splitting and filename expansion on the unquoted variable, which can lead…
When to Prefer $(…) Over Backticks The $(…) syntax for command substitution, also known as the dollar-paren syntax, has several advantages over using backticks “: $(…) substitutions are more readable and less visually cluttered in most cases Nested substitutions and quoting work better with $(…) compared to backticks The $(…) style is supported in all…
Getting Started with Command Substitution Definition and Basic Syntax of Command Substitution in Bash Command substitution in Bash allows you to assign the output of a command to a variable or pass it as an argument to another command. It substitutes the command with its output. The basic syntax for command substitution is: $(command) `command`…
The Origins of Man Page Sections in Early Unix In the early days of Unix, developers needed a way to organize documentation as the system grew more complex. The lack of structure made it hard for users to find what they needed. The man page system introduced in Version 4 Unix in 1973 brought order…
Why Man Pages Matter Man pages serve as the primary documentation for programs and scripts on Linux and Unix-based systems. They provide essential reference information that enables users to understand and effectively utilize commands and applications. Man pages are vital for ensuring the usability of custom scripts and software in several key ways: Providing essential…