Scripting

When to Quote Variables Quoting variables in shell scripts is vital for strings containing spaces, special characters, and to prevent unwanted expansions. Quoting allows strings to be passed verbatim to commands and assignments without interference from the shell. Strings with Spaces or Special Characters Double quotes should surround strings containing spaces, tabs, or newlines to…

Potential Pitfalls of Shell Variables Shell variables are used to store data in bash and other Unix shell scripts. However, there are some key portability concerns and pitfalls to be aware of when working with shell variables across different systems and environments. Environment Differences Across Systems A major portability consideration with shell variables is differences…

The Problem: Doing Math Without a GUI Working without a graphical user interface poses challenges for performing mathematical and scientific computations. The lack of interactive visualizations, plotting capabilities, and other features often relied upon in math applications can make calculations tedious and counterintuitive. However, Linux’s built-in scripting languages provide powerful programmatic interfaces for a wide…

Checking Multiple Conditions in if Statements Bash scripts often need to check multiple conditions before executing commands. The bash if statement allows checking multiple conditions using Boolean operators AND and OR. The AND operator (&&) evaluates as true if both the conditions on either side of it are true. The OR operator (||) evaluates as…

Bash conditionals allow scripts to make decisions and execute code conditionally based on the status of files, variables, and other criteria. However, these powerful tools come with rigid syntax rules that are easy to violate if spacing is not meticulous. Innocent-looking spaces, tabs, and trailing whitespace can lead to frustrating errors that cause bash scripts…

Reducing Complexity with Case Statements Conditional logic is ubiquitous in programming. We often need to execute different code blocks based on the state of variables or the flow of program execution. However, nested if-else statements and chained conditional logic can quickly become complex and hard to reason about. Case statements provide a way to simplify…

Remote X11 connections allow a user to launch graphical applications on a remote server and have the windows display securely on their local machine. To enable this functionality, the X11 forwarding feature must be enabled in the SSH daemon on the remote server. Common methods to achieve this include editing the /etc/ssh/sshd_config file to set…

The Problem: Inconsistent Variable Usage Shell scripts allow variables to be accessed with or without braces (e.g. $foo vs ${foo}). This flexibility can lead to inconsistencies and unexpected behavior if not used carefully. Using braces around variables provides clarity, avoids naming conflicts, and enables more robust usage. Benefits of Using Braces Using braces { and…

Escaping Special Characters in Filenames Filenames containing special characters like spaces, asterisks, and parentheses can cause errors when used with commands in shells like Bash. The shell attempts to interpret these characters instead of treating them as literals which leads to unintended behavior. For example, an asterisk is used to wildcard match any characters in…

The Pitfalls of Quoting and Special Characters in find -exec The find command in Linux allows users to search for files matching certain criteria and then perform actions on those files using the -exec option. However, properly quoting arguments and handling special characters in filenames can be tricky when using -exec. If arguments are not…