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Jessica Brown

A blog by Jessica Brown in CodeName Blogs

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Tutorials

Regular Expression Tutorial (TOC)

Regular Expressions Tutorial Table of Contents Regular Expression Tutorial pg 1 Word Boundaries pg 10 Understanding Atomic Grouping in Regular Expressions pg 19 Different Regular Expression Engines pg 2 Alternation with the Vertical Bar or Pipeline Symbol pg 11 Understanding Lookahead and Lookbehind in Regular Expressions (Lookaround) pg 20 Literal Characters pg 3 Optional Items pg 12 Testing Multiple Conditions on the Same Part of a String with Lookaround pg 21 Special Characters pg 4 Repetitio
Linux

Introduction to SALT: A Unified Platform for Infrastructure Automation

SaltStack (SALT): A Comprehensive Overview SaltStack, commonly referred to as SALT, is a powerful open-source infrastructure management platform designed for scalability. Leveraging event-driven workflows, SALT provides an adaptable solution for automating configuration management, remote execution, and orchestration across diverse infrastructures. This document offers an in-depth guide to SALT for both technical teams and business stakeholders, demystifying its features and applications. What
Webhosting

Cloudflare R2 Outage Incident Report - February 6, 2025

Overview On Thursday, February 6, 2025, multiple Cloudflare services, including R2 object storage, experienced a significant outage lasting 59 minutes. This incident resulted in complete operational failures against R2 and disruptions to dependent services such as Stream, Images, Cache Reserve, Vectorize, and Log Delivery. The root cause was traced to human error and inadequate validation safeguards during routine abuse remediation procedures. Impact Summary Incident Duration: 08:14 UTC to 09:13
Book Recommendations

Why Every SysAdmin Should Understand ISO/IEC 27001:2022

In today’s digital landscape, the role of a System Administrator (SysAdmin) extends far beyond server uptime and software updates. With cyber threats evolving daily, understanding key information security standards like ISO/IEC 27001:2022 is no longer optional, it’s essential. This international standard provides a robust framework for establishing, implementing, maintaining, and continuously improving an Information Security Management System (ISMS). For SysAdmins, mastering ISO/IEC 27001 isn’t
Book Recommendations

📚 Recommended Cloud Computing Books to Read for Jan. 31, 2025

Cloud Computing and Security Author(s): Xingming Sun, Alex Liu, Han-Chieh Chao, Elisa Bertino Subject: cloud_computing Title: Unraveling the Intricacies of Cloud Computing a Review of 'Cloud Computing and Security' by Xingming Sun, Alex Liu, Han-Chieh Chao, Elisa Bertino A Definitive Guide to the Cloud No phenomenon has revolutionized the world of Information Technology in the 21st century quite like cloud computing. It's all around us, powering our personal devices, organizational infrastructu
Book Recommendations

📚 Recommended Linux Books to Read for Jan. 31, 2025

Linux in a Nutshell Author(s): Jessica Perry Hekman, Ellen Siever, Aaron Weber, Stephen Figgins, Robert Love, Arnold Robbins, Stephen Spainhour Linux in a Nutshell: An In-Depth Review "Linux in a Nutshell", is a prodigious technical reference book penned by an impressive team of authors – Jessica Perry Hekman, Ellen Siever, Aaron Weber, Stephen Figgins, Arnold Robbins, Stephen Spainhour and Robert Love. It provides a comprehensive and utterly engaging tour of the Linux operating system for begin
Book Recommendations

📚 Recommended Servers Books to Read for Jan. 31, 2025

Web Server Programming Author(s): Neil Gray Subject: servers 'Web Server Programming' Explored: An Enlightening Dive into Digital Engineering As someone deeply entrenched in the world of literature, there are books that unravel their mysteries instantly and others that unfold their knowledge meticulously. Falling gleefully into the latter category is Web Server Programming by Neil Gray. In this technologically intensive era, Gray masterfully deciphers the art of web server programming, venturing
Book Recommendations

📚 Recommended Programming Books to Read for Jan. 31, 2025

Reconfigurable Processor Array a Bit Sliced Parallel Computer (USA) Author(s): A. Rushton Subject: programming The Breakthrough of Parallel Computing: A Review of A. Rushton's 'Reconfigurable Processor Array a Bit Sliced Parallel Computer (USA)' In the ever-evolving world of technology, keeping up with the innovation and concepts that define the landscape can be a challenge. Yet, in his book, 'Reconfigurable Processor Array - A Bit Sliced Parallel Computer (USA)', A. Rushton provides a solid f
Ethical Hacking

Flipper Zero: The Ultimate Portable Hacking & Security Tool

What is Flipper Zero? Flipper Zero is a multi-functional portable cybersecurity tool designed for penetration testing, signal analysis, and hardware interaction. It is compact, open-source, and packed with features that make it a must-have for security professionals, ethical hackers, and tech enthusiasts. With its ability to read, store, emulate, and analyze wireless signals, Flipper Zero is the Swiss Army knife of hacking tools, helping users test security vulnerabilities, explore digital acces
Linux

Enhancing Your Security: A Guide to Using YubiKey 5 NFC for SSH on Linux

Why You Need a YubiKey for SSH Security If you're serious about securing your Linux SSH connections, relying on password-based authentication or even traditional SSH keys isn’t enough. Hardware security keys like the Yubico YubiKey 5 NFC offer phishing-resistant authentication, adding an extra layer of security to your workflow. With support for multiple authentication protocols (FIDO2, U2F, OpenPGP, and PIV), this compact device helps developers, system admins, and cybersecurity professionals p
Tutorials

JavaScript Skill Progression: The Path from Beginner to Extreme

{{#anchor-lvl1}} Level 1 - The Foundations: Understanding JavaScript Basics Introduction to JavaScript: What it is, how it works, and where it runs (browsers, Node.js). (part 1) JavaScript Variables & Data Types: var, let, const, and primitive types (String, Number, Boolean, Undefined, Null, Symbol, BigInt). (part 2) JavaScript Operators & Expressions: Arithmetic, comparison, logical, and assignment operators. (part 3) JavaScript Conditional Statements: if, else, switch. (part 4) Jav
Tutorials

Harden and Secure Linux Servers by Level (1 - 6)

Securing a Linux server is an ongoing challenge. Every day, bad actors attempt to penetrate systems worldwide, using VPNs, IP spoofing, and other evasion tactics to obscure their origins. The source of an attack is often the least of your concerns, what matters most is implementing strong security measures to deter threats and protect your infrastructure. Hardening your servers not only makes them more resilient but also forces attackers to either move on or, ideally, abandon their efforts altog
Tutorials

Free-Spacing Mode in Regular Expressions: Improving Readability (Page 27)

Free-spacing mode, also known as whitespace-insensitive mode, allows you to write regular expressions with added spaces, tabs, and line breaks to make them more readable. This mode is supported by many popular regex engines, including JGsoft, .NET, Java, Perl, PCRE, Python, Ruby, and XPath. How to Enable Free-Spacing Mode To activate free-spacing mode, you can use the mode modifier (?x) within your regex. Alternatively, many programming languages and applications offer options to enable free-spa
Tutorials

Adding Comments to Regular Expressions: Making Your Regex More Readable (Page 26)

Regular expressions can quickly become complex and difficult to understand, especially when dealing with long patterns. To make them easier to read and maintain, many modern regex engines allow you to add comments directly into your regex patterns. This makes it possible to explain what each part of the expression does, reducing confusion and improving readability. How to Add Comments in Regular Expressions The syntax for adding a comment inside a regex is: (?#comment) The text inside the parent
Tutorials

Understanding POSIX Bracket Expressions in Regular Expressions (Page 25)

POSIX bracket expressions are a specialized type of character class used in regular expressions. Like standard character classes, they match a single character from a specified set of characters. However, they offer additional features such as locale support and unique character classes that aren't found in other regex flavors. Key Differences Between POSIX Bracket Expressions and Standard Character Classes POSIX bracket expressions are enclosed in square brackets ([]), just like regular charact
Tutorials

XML Schema Character Classes and Subtraction Explained (Page 24)

XML Schema introduces unique character classes and features not commonly found in other regular expression flavors. These classes are particularly useful for validating XML names and values, making XML Schema regex syntax essential for working with XML data. Special Character Classes in XML Schema In addition to the six standard shorthand character classes (e.g., \d for digits, \w for word characters), XML Schema introduces four unique shorthand character classes designed specifically for XML na
Tutorials

Using If-Then-Else Conditionals in Regular Expressions (Page 23)

Conditional logic isn’t limited to programming languages — many modern regular expression engines allow if-then-else conditionals. This feature lets you apply different matching patterns based on a condition. The syntax for conditionals is: (?(condition)then|else) If the condition is met, the then part is attempted. If the condition is not met, the else part is applied instead. You can omit the else part if it’s not needed. Conditional Syntax and How It Works The syntax for if-then-else conditio
Tutorials

Understanding the \G Anchor in Regular Expressions (Page 22)

The \G anchor is a powerful tool in regular expressions, allowing matches to continue from the point where the previous match ended. It behaves similarly to the start-of-string anchor \A on the first match attempt, but its real utility shines when used in consecutive matches within the same string. How the \G Anchor Works The anchor \G matches the position immediately following the last successful match. During the initial match attempt, it behaves like \A, matching the start of the string. On s
Tutorials

Testing Multiple Conditions on the Same Part of a String with Lookaround (Page 21)

In regular expressions, it’s common to need a match that satisfies multiple conditions simultaneously. This is where lookahead and lookbehind, collectively known as lookaround assertions, come in handy. These zero-width assertions allow the regex engine to test conditions without consuming characters in the string, making it possible to apply multiple requirements to the same portion of text. Why Lookaround Is Essential Let’s say you want to match a six-letter word that contains the sequence “ca
Tutorials

Understanding Lookahead and Lookbehind in Regular Expressions (Lookaround) (Page 20)

Lookahead and lookbehind, often referred to collectively as "lookaround," are powerful constructs introduced in Perl 5 and supported by most modern regular expression engines. They are also known as zero-width assertions because they don’t consume characters in the input string. Instead, they simply assert whether a certain condition is true at a given position without including the matched text in the overall match result. Lookaround constructs allow you to build more flexible and efficient reg
Tutorials

Understanding Atomic Grouping in Regular Expressions (Page 19)

Atomic grouping is a powerful tool in regular expressions that helps optimize pattern matching by preventing unnecessary backtracking. Once the regex engine exits an atomic group, it discards all backtracking points created within that group, making it more efficient. Unlike regular groups, atomic groups are non-capturing, and their syntax is represented by (?:?>group). Lookaround assertions like (?=...) and (?!...) are inherently atomic as well. Atomic grouping is supported by many popular r
Tutorials

Possessive Quantifiers (Page 18)

When working with repetition operators (also known as quantifiers) in regular expressions, it’s essential to understand the difference between greedy, lazy, and possessive quantifiers. Greedy and lazy quantifiers affect the order in which the regex engine tries to match permutations of the pattern. However, both types still allow the regex engine to backtrack through the pattern to find a match. Possessive quantifiers take a different approach—they do not allow backtracking once a match is made,
Tutorials

Regex Matching Modes (Page 17)

Most regular expression engines discussed in this tutorial support the following four matching modes: Modifier Description /i Makes the regex case-insensitive. /s Enables "single-line mode," making the dot (.) match newlines. /m Enables "multi-line mode," allowing caret (^) and dollar ($) to match at the start and end of each line. /x Enables "free-spacing mode," where whitespace is ignored, and # can be used for comments. Specifying Modes Inside The Regular Expression You can specify these mode
Tutorials

Unicode Regular Expressions (Page 16)

Unicode regular expressions are essential for working with text in multiple languages and character sets. As the world becomes more interconnected, supporting Unicode is increasingly important for ensuring that software can handle diverse text inputs. What is Unicode? Unicode is a standardized character set that encompasses characters and glyphs from all human languages, both living and dead. It aims to provide a consistent way to represent characters from different languages, eliminating the ne
Tutorials

Named Capturing Groups (Page 15)

Named capturing groups allow you to assign names to capturing groups, making it easier to reference them in complex regular expressions. This feature is available in most modern regular expression engines. Why Use Named Capturing Groups? In traditional regular expressions, capturing groups are referenced by their numbers (e.g., \1, \2). As the number of groups increases, it becomes harder to manage and understand which group corresponds to which part of the match. Named capturing groups solve th

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