Compression reduces the size of a file by encoding its contents more efficiently. On Linux, three compressors dominate: gzip, bzip2, and xz. Each is a general-purpose compressor with a different trade-off between speed and compression ratio. gzip is the fastest and the most widely supported. bzip2 compresses better but is slower. xz compresses the best…
tar is the standard archiving tool on Linux. It bundles many files and directories into a single archive file, preserving their paths, permissions, ownership, timestamps, and directory structure. The name comes from “tape archive,” a reference to its origins as a tool for writing backups to magnetic tape, but the format survived the tape era…
awk is a complete programming language designed for text processing. Where grep selects lines and sed transforms them, awk understands fields. It splits each input line into columns, gives each column a name, and lets you write expressions and actions that operate on those columns. A single awk command can find the lines that match…
sed is the stream editor. It reads input line by line, applies a set of editing commands to each line, and writes the result to standard output. Unlike an interactive editor, sed is not meant for hand-editing a file. It is a filter: it takes a stream of text, transforms it according to a script,…
grep is the command-line equivalent of the find function in a text editor: it searches input for lines that match a pattern and prints the matching lines to standard output. It is one of the most frequently used commands in Linux administration, and the LFCS exam tests it as part of the “Search files and…
Props flow down from parent to child. Events flow up from child to parent. When a child component needs to tell its parent that something happened — a button was clicked, a value changed, a form was submitted — it emits an event. The parent listens for that event and reacts. This is the second…
In Vue 3.4 and earlier, destructuring props was a known footgun. The official documentation warned against it, and the ESLint plugin had a rule to catch it. The reason was simple: defineProps() returns a reactive object, and destructuring it reads the current value and stores it in a plain variable. The variable is no longer…
Props are the primary mechanism for passing data from a parent component to a child component. In Vue 3’s <script setup>, the defineProps() macro is the way to declare them. It is a compiler macro, not a function that runs at runtime. The compiler reads the declaration, generates the equivalent runtime props option, and removes…
Vue’s reactivity system is automatic, and most of the time that is exactly what you want. You change a ref, and the component re-renders. You read a ref in a template, and Vue records that the component depends on it. But when a component re-renders too often, or not often enough, the automatic behavior becomes…
A Vue component is not a static piece of markup. It is created, mounted into the DOM, updated when its reactive state changes, and eventually unmounted. Each of these phases is a moment when the component may need to do something: fetch data after it appears, react to a prop change, clean up a timer…