Create part 1 of shells and scripts notes

src/content/blog/shells-and-scripts-part-1.md

@@ -0,0 +1,155 @@
+---
+title: shells and scripts part 1
+description: Theory behind working with Linux via a CLI and automating various tasks
+pubDate: 2023-08-28T18:24:05.514Z
+draft: true
+categories:
+  - learning modern linux
+tags:
+  - linux
+  - notes
+---
+
+Hey folks!
+
+This post contains my notes from the third chapter of _Learning Modern Linux_ book written by Michael Hausenblas. Let's just jump into it!
+
+## Ways of working with a CLI
+
+There are two ways in which a user can work with Linux via a CLI:
+
+- **Manual** via a terminal or a pseudo-terminal such as `tty`, where a human inputs commands and checks their output
+- **Automatic** by utilising shell scripts, which come in handy for repetitive tasks
+
+## Terminal and Terminal Emulator
+
+**Terminal** is an electronic device which generally consists of a keyboard and a monitor for inputting commands and data into a computer and inspecting the output of entered commands respectively.
+
+**Terminal Emulator** is an application that mimics the behaviour of a physical terminal usually via a graphical user interface or a full-screen console.
+
+## Shell
+
+**Shell** is a program that interprets and executes incoming commands, handles input/output data and enables the user to enter these commands both manually and automatically via scripts.
+
+## Streams
+
+### Definition
+
+**Streams** serve as a means of transporting input, output, and error data. In Linux and other Unix-like systems, every process has access to three **file descriptors**:
+
+- 0 for `stdin`
+- 1 for `stdout`
+- 2 for `stderr`
+
+### Redirecting to other destinations
+
+By default, `stdin` is connected to the keyboard and the other two are connected to the screen. It's possible to redirect a stream elsewhere by adding `$FD>`, where `$FD` is an appropriate file descriptor (see: list above).
+
+If you omit `$FD`, `stdout` will get redirected to the specified destination. If you want to redirect both `stdout` and `stderr` to the same destination, use `&>`. And if you want to ignore a certain stream, redirect it to `/dev/null`.
+
+### Special characters
+
+- `&` (ampersand) will run a command in the background
+- `\` (backslash) allows you to continue writing a command in a new line
+- `|` (pipe) allows you to pipe one command's `stdout` into the following command's `stdin`
+
+## Variables
+
+Shell variables, just like in pretty much any other programming language, are used to store a piece of data under a symbolic name.
+
+We can specify two types of variables:
+
+- **Environment variables** that are used to configure a value in some script from outside said code
+- **Shell variables** that are limited to the execution context of a given script
+
+Here's how to create a shell variable:
+
+```sh
+set NICE_NUMBER=69
+```
+
+And here's how to create an environment variable:
+
+```sh
+export ANOTHER_NICE_NUMBER=420
+```
+
+Here's how to print a variable's value:
+
+```sh
+echo $VARIABLE_NAME_HERE
+```
+
+Select environment and shell variables:
+
+- `PATH` - list of paths to search for executables to run
+- `HOSTNAME` - name of the device
+- `PWD` - absolute path to the current working directory
+- `USER` - current user's username
+- `$` - current PID
+- `?` - last task's exit code
+
+Speaking of exit codes...
+
+## Exit Codes
+
+Every process is expected to return a status code after exiting. Code `0` means a **successful execution**, whereas every code greater than or equal `1` means some sort of a **failure**.
+
+## Job Control
+
+By default, every command you execute runs in **the foreground**, meaning it takes control over the keyboard and the screen. If you want to start a task in **the background**, you have to append a `&` to the command, or press `Ctrl+Z` while the task is running in the foreground.
+
+## Modern command replacements and other utils
+
+- [`exa`](https://the.exa.website/) as a replacement for `ls -l`
+- [`bat`](https://github.com/sharkdp/bat) as a replacement for `cat`
+- [`ripgrep (rg)`](https://github.com/BurntSushi/ripgrep) as a replacement for... well, `grep`
+- [`gtop`](https://github.com/aksakalli/gtop) as a performance monitor in your CLI
+- [`curlie`](https://github.com/rs/curlie) as a modern enhancement of `curl`
+
+Feel free to check out [the modern-unix repo](https://github.com/ibraheemdev/modern-unix) for more examples.
+
+## Navigation
+
+Here's a list of some key combinations to help you navigate around your CLI:
+
+- `Ctrl + A` moves the cursor to the start of the line
+- `Ctrl + E` moves the cursor to the end of the line
+- `Left Alt + F` moves the cursor forward by a word
+- `Left Alt + B` moves the cursor backward by a word
+- `Ctrl + U` removes all the characters on the left-hand side of a cursor
+- `Ctrl + K` removes all the characters on the right-hand side of a cursor
+
+## File content CRUD operations
+
+### Create a file
+
+```sh
+touch cool-file.txt
+```
+
+### Read a file
+
+```sh
+cat cool-file.txt
+```
+
+### Overwrite a file's content
+
+```sh
+echo 'New file content' > cool-file.txt
+```
+
+### Append content to a file
+
+```sh
+echo 'Even more new content' >> cool-file.txt
+```
+
+(There's no need to add a newline character manually)
+
+### Delete a file
+
+```sh
+rm cool-file.txt
+```

src/pages/rss.xml.js

@@ -3,14 +3,16 @@ import { getCollection } from 'astro:content';
 import { SITE_TITLE, SITE_DESCRIPTION } from '../consts';
 
 export async function get(context) {
-	const posts = await getCollection('blog');
-	return rss({
-		title: SITE_TITLE,
-		description: SITE_DESCRIPTION,
-		site: context.site,
-		items: posts.map((post) => ({
-			...post.data,
-			link: `/blog/${post.slug}/`,
-		})),
-	});
+  const posts = (await getCollection('blog')).sort(
+    (a, b) => b.data.pubDate.valueOf() - a.data.pubDate.valueOf()
+  );
+  return rss({
+    title: SITE_TITLE,
+    description: SITE_DESCRIPTION,
+    site: context.site,
+    items: posts.map((post) => ({
+      ...post.data,
+      link: `/blog/${post.slug}/`
+    }))
+  });
 }