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Jessica Brown

A blog by Jessica Brown in CodeName Blogs

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Tutorials

Grouping with Round Brackets (Page 14)

In regular expressions, round brackets (()) are used for grouping. Grouping allows you to apply operators to multiple tokens at once. For example, you can make an entire group optional or repeat the entire group using repetition operators. Basic Usage For example: Set(Value)? This pattern matches: "Set" "SetValue" The round brackets group "Value", and the question mark makes it optional. Note: Square brackets ([]) define character classes. Curly braces ({}) specify repetition counts. Only ro
Tutorials

Repetition with Star and Plus (Page 13)

In addition to the question mark, regex provides two more repetition operators: the asterisk (*) and the plus (+). Basic Usage The * (star) matches the preceding token zero or more times. The + (plus) matches the preceding token one or more times. For example: <[A-Za-z][A-Za-z0-9]*> This pattern matches HTML tags without attributes: <[A-Za-z] matches the first letter. [A-Za-z0-9]* matches zero or more alphanumeric characters after the first letter. This regex will match tags like: <
Tutorials

Optional Items (Page 12)

The question mark (?) makes the preceding token in a regular expression optional. This means that the regex engine will try to match the token if it is present, but it won’t fail if the token is absent. Basic Usage For example: colou?r This pattern matches both "colour" and "color." The u is optional due to the question mark. You can make multiple tokens optional by grouping them with round brackets and placing a question mark after the closing bracket: Nov(ember)? This regex matches both "Nov"
Tutorials

Alternation with the Vertical Bar or Pipe Symbol (Page 11)

Previously, we explored how character classes allow you to match a single character out of several possible options. Alternation, on the other hand, enables you to match one of several possible regular expressions. The vertical bar or pipe symbol (|) is used for alternation. It acts as an OR operator within a regex. Basic Syntax To search for either "cat" or "dog," use the pattern: cat|dog You can add more options as needed: cat|dog|mouse|fish The regex engine will match any of these options. Fo
Tutorials

Word Boundaries (Page 10)

The \b metacharacter is an anchor, similar to the caret (^) and dollar sign ($). It matches a zero-length position called a word boundary. Word boundaries allow you to perform “whole word” searches in a string using patterns like \bword\b. What is a Word Boundary? A word boundary occurs at three possible positions in a string: Before the first character if it is a word character. After the last character if it is a word character. Between two characters where one is a word character and the ot
Tutorials

Start of String and End of String Anchors (Page 9)

In previous sections, we explored how literal characters and character classes operate in regular expressions. These match specific characters in a string. Anchors, however, are different. They match positions in the string rather than characters, allowing you to "anchor" your regex to the start or end of a string or line. Using the Caret (^) Anchor The caret (^) matches the position before the first character of the string. For example: ^a applied to "abc" matches "a." ^b does not match "abc"
Tutorials

The Dot Matches (Almost) Any Character (Page 8)

The dot, or period, is one of the most versatile and commonly used metacharacters in regular expressions. However, it is also one of the most misused. The dot matches any single character except for newline characters. In most regex flavors discussed in this tutorial, the dot does not match newlines by default. This behavior stems from the early days of regex when tools were line-based and processed text line by line. In such cases, the text would not contain newline characters, so the dot could
Tutorials

Character Classes or Character Sets (Page 7)

Character classes, also known as character sets, allow you to define a set of characters that a regex engine should match at a specific position in the text. To create a character class, place the desired characters between square brackets. For instance, to match either an a or an e, use the pattern [ae]. This can be particularly useful when dealing with variations in spelling, such as in the regex gr[ae]y, which will match both "gray" and "grey." Key Points About Character Classes: A character
Tutorials

First Look at How a Regex Engine Works Internally (Page 6)

Understanding how a regex engine processes patterns can significantly improve your ability to write efficient and accurate regular expressions. By learning the internal mechanics, you’ll be better equipped to troubleshoot and refine your regex patterns, reducing frustration and guesswork when tackling complex tasks. Types of Regex Engines There are two primary types of regex engines: Text-Directed Engines (also known as DFA - Deterministic Finite Automaton) Regex-Directed Engines (also known as
Tutorials

Non-Printable Characters (Page 5)

Regular expressions can also match non-printable characters using special sequences. Here are some common examples: \t: Tab character (ASCII 0x09) \r: Carriage return (ASCII 0x0D) \n: Line feed (ASCII 0x0A) \a: Bell (ASCII 0x07) \e: Escape (ASCII 0x1B) \f: Form feed (ASCII 0x0C) \v: Vertical tab (ASCII 0x0B) Keep in mind that Windows text files use "\r\n" to terminate lines, while UNIX text files use "\n". Hexadecimal and Unicode Characters You can include any character in your regex usin
Tutorials

Special Characters (Page 4)

To go beyond matching literal text, regex engines reserve certain characters for special functions. These are known as metacharacters. The following characters have special meanings in most regex flavors discussed in this tutorial: [ \ ^ $ . | ? * + ( ) If you need to use any of these characters as literals in your regex, you must escape them with a backslash (\). For instance, to match "1+1=2", you would write the regex as: 1\+1=2 Without the backslash, the plus sign would be interpreted as a q
Tutorials

Literal Characters (Page 3)

The simplest regular expressions consist of literal characters. A literal character is a character that matches itself. For example, the regex «a» will match the first occurrence of the character "a" in a string. Consider the string "Jack is a boy": this pattern will match the "a" after the "J". It’s important to note that the regex engine doesn’t care where the match occurs within a word unless instructed otherwise. If you want to match entire words, you’ll need to use word boundaries, a concep
Tutorials

Different Regular Expression Engines (Page 2)

A regular expression engine is a software component that processes regex patterns, attempting to match them against a given string. Typically, you won’t interact directly with the engine. Instead, it operates behind the scenes within applications and programming languages, which invoke the engine as needed to apply the appropriate regex patterns to your data or files. Variations Across Regex Engines As is often the case in software development, not all regex engines are created equal. Different
Tutorials

Regular Expression Tutorial (Page 1)

Table of Contents Regular Expression Tutorial Different Regular Expression Engines Literal Characters Special Characters Non-Printable Characters First Look at How a Regex Engine Works Internally Character Classes or Character Sets The Dot Matches (Almost) Any Character Start of String and End of String Anchors Word Boundaries Alternation with the Vertical Bar or Pipe Symbol Optional Items Repetition with Star and Plus Grouping with Round Brackets Named Capturing Groups Unicode Re
Linux

Walkthrough: Setting Up BackupNinja to Back Up a Website on Linux to a Windows Machine Using SMB

Prerequisites Before proceeding, ensure the following components are in place: BackupNinja Installed Verify BackupNinja is installed on your Linux server. Command: sudo apt update && sudo apt install backupninja Common Errors & Solutions: Error: "Unable to locate package backupninja" Ensure your repositories are up-to-date: sudo apt update Enable the universe repository on Ubuntu/Debian systems: sudo add-apt-
Programming

17 Subtle Rules of Software Engineering

List By: Miko Pawlikowski  Descriptions By: Jessica Brown Published: December 29, 2024 Software engineering is a discipline that balances technical precision, creativity, and collaboration. These 17 subtle rules provide insights to improve the quality of code, foster teamwork, and guide sustainable practices. 0. Stop Falling in Love with Your Own Code When you become too attached to your code, you may resist valuable feedback or overlook its flaws. Always prioritize the quality of the solution
Programming

Understanding the MVVM Structure in Programming

The Model-View-ViewModel (MVVM) architectural pattern is widely used in modern software development for creating applications with a clean separation between user interface (UI) and business logic. Originating from Microsoft's WPF (Windows Presentation Foundation) framework, MVVM has found applications in various programming environments, including web development frameworks like Vue.js, Angular, and React (when combined with state management libraries). What is MVVM? The MVVM pattern
Programming

Creating a VueJS Application from Scratch on Windows and Linux

Vue.js is a versatile and progressive JavaScript framework for building user interfaces. Its simplicity and powerful features make it an excellent choice for modern web applications. In this article, we will walk through creating a VueJS application from scratch on both Windows and Linux. Prerequisites Before starting, ensure you have the following tools installed on your system: For Windows: Node.js and npm Download and install from Node.js official website.
Webhosting

Error 413: Handling Content Too Large for a Website

Uploading large files to a website can fail due to server-side limitations on file size. This issue is typically caused by default configurations of web servers like Nginx or Apache, or by PHP settings for sites using PHP. This guide explains how to adjust these settings and provides detailed examples for common scenarios. For Nginx Nginx limits the size of client requests using the client_max_body_size directive. If this value is exceeded, Nginx will return a 413 Request Entity T
Linux

What Will 2025 Bring for Linux Operating Systems?

The Linux operating system has continually evolved from a niche platform for tech enthusiasts into a critical pillar of modern technology. As the backbone of everything from servers and supercomputers to mobile devices and embedded systems, Linux drives innovation across industries. Looking ahead to 2025, several key developments and trends are set to shape its future. Linux in Cloud and Edge Computing As the foundation of cloud infrastructure, Linux distributions such as Ubuntu Server
Hosting

Why I Choose IONOS Web Hosting

As someone who has worked with numerous hosting providers over the years, I can confidently say that IONOS stands out as a superior choice for web hosting. Their servers are not only robust but also incredibly cost-effective, offering features and performance that rival much pricier competitors. Let me share why I’ve been so impressed with their services and why you might want to consider them for your own projects. Exceptional Features at an Affordable Price IONOS provides a wide rang
Theories

The Dead Internet Theory: A Digital Ghost Town or a New Reality?

The internet is deeply embedded in modern life, serving as a platform for communication, commerce, education, and entertainment. However, the Dead Internet Theory questions the authenticity of this digital ecosystem. Proponents suggest that much of the internet is no longer powered by genuine human activity but by bots, AI-generated content, and automated systems. This article delves into the theory, its claims, evidence, counterarguments, and broader implications. Understanding the Dead In

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