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Posted on Aug 23, 2023 Edited on Aug 23, 2023 Originally published at docs.deploypro.dev

Bash, the magic that empowers the Cloud

#bash #deployments #linux #deploypro

Hello Coders!

This article is not about ML, Generative AI, automation, or any other hot topic. It’s about Bash, also known as Bourne Again Shell the workhorse that empowers Cloud Computing and Services like AWS, GCP, Azure or Digital Ocean.

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With decent Bash knowledge, anyone can manage a Linux system with ease, deploy projects LIVE, schedule backups, and execute maintenance tasks using the CRON System. If this sounds like something useful, let’s move forward and point out a few Bash-related topics and tools.

What is Bash?

Bash, short for “Bourne Again Shell” is a command-line interface and scripting language used in Unix-like operating systems. It provides a way to interact with the operating system by running commands, and it also supports writing scripts to automate tasks.

Getting Started

Open a terminal on your Linux system. This is where you’ll interact with Bash.
Type a command and press Enter to execute it. For example, ls lists files in the current directory.
Arguments can be added after the command, like ls -l to list files in long format.

Basic Commands

ls: List files and directories in the current location.
cd: Change directory.
pwd: Print the current working directory.
mkdir: Create a new directory.
touch: Create an empty file.
cp: Copy files or directories.
mv: Move or rename files or directories.
rm: Remove files or directories (use with caution).

Variables

Bash uses variables to store and manipulate data.

name="John"
echo "Hello, $name!"

Input and Output

echo: Print text to the screen.
read: Read input from the user.

echo "What's your name?"
read name
echo "Hello, $name!"

Conditional Statements

Bash supports if statements for conditional execution.

age=25
if [ "$age" -lt 18 ]; then
    echo "You're a minor."
else
    echo "You're an adult."
fi

Loops

for fruit in apple banana orange; do
    echo "I like $fruit."
done

Functions

greet() {
    echo "Hello, $1!"
}
greet "Alice"

Simple Calculator Script

#!/bin/bash
read -p "Enter first number: " num1
read -p "Enter second number: " num2
sum=$((num1 + num2))
echo "Sum: $sum"

Bash & Linux Tools

This section presents a few tools we can use to manage different aspects of a Linux box like backups, text browsing, and file editing.

Cron System

The cron system is a time-based job scheduling mechanism in Unix-like operating systems. It allows you to automate repetitive tasks by scheduling them to run at specific intervals. The term “cron” comes from the Greek word “chronos,” meaning time.

Components of the Cron System

Cron Daemon (cron): The cron daemon is a background service that manages the scheduling and execution of cron jobs. It constantly checks the system's crontab files to determine when to run scheduled tasks.
Cron Jobs: A cron job is a command or script that you want to run automatically at a specified time or interval. Each cron job consists of a command and a schedule defined by cron syntax.

Cron Syntax: Cron uses a specific syntax to define when a job should be executed. The syntax consists of five fields (plus an optional command field):

* * * * * command_to_run
| | | | |
| | | | +----- Day of the week (0 - 6) (Sunday = 0)
| | | +------- Month (1 - 12)
| | +--------- Day of the month (1 - 31)
| +----------- Hour (0 - 23)
+------------- Minute (0 - 59)

Cron Samples

Run a Script Every Night at Midnight

0 0 * * * /path/to/script.sh

Send System Statistics Every Hour

0 * * * * /usr/bin/collect_stats.sh

cURL — Client URL

curl (short for "Client URL") is a command-line tool and library for transferring data with URLs. It supports various protocols, including HTTP, HTTPS, FTP, FTPS, SCP, SFTP, LDAP, and more. curl is widely used to interact with web services, download files, and perform data transfers from the command line in Unix-like operating systems.

cURL Samples

Downloading a File

curl -O https://www.example.com/file.txt

Fetching Only Headers

curl -I https://www.example.com

Sending POST Data

curl -X POST -d "key=value" https://www.example.com/post_endpoint

Gzip

gzip is a command-line utility used to compress and decompress files in Unix-like operating systems. It is named after the "GNU zip" project, which aims to provide a free and efficient replacement for the older compress utility.

Basic Usage

gzip [options] file

Gzip Samples

Compressing a File

gzip file.txt

Decompressing a File

gzip -d file.txt.gz

Testing Compressed Files

gzip -t file.txt.gz

gzip is commonly used to compress individual files and is often used in combination with other tools and utilities. It produces files with the .gz extension and these compressed files can save disk space and accelerate data transfer when distributing or storing files.

Lynx

lynx is a text-based web browser that allows users to browse the internet and view web pages from the command line in Unix-like operating systems. It's a versatile tool for accessing information from websites without requiring a graphical user interface.

While it doesn’t render images or complex layouts like modern graphical browsers, it’s useful for quick access to text-based content, checking links, and accessing web resources in a terminal environment.

Basic Usage

lynx [options] [URL]

Lynx Samples

Viewing a Web Page

lynx https://www.example.com

Viewing Page Source

lynx -source https://www.example.com

Viewing Plain Text Version

lynx -dump https://www.example.com

Rsync

Using the rsync command in Bash, you can synchronize the contents of a directory between two locations, either locally or across different machines over a network.

Basic Usage

rsync [options] source_directory destination

Rsync Samples

Local Sync

rsync -av source/ destination/

Remote Sync over SSH

rsync -av source/ user@remote_host:destination/

Excluding Files with Progress Indicators

rsync -av --progress --exclude '*.txt' source/ destination/

These examples cover some of the common use cases for rsync. The command offers many more options and functionalities for more complex synchronization scenarios.

Wget

wget is a command-line utility used for downloading files from the internet. It supports various protocols, including HTTP, HTTPS, FTP, and FTPS. wget is commonly used to retrieve files and web content from the command line in Unix-like operating systems.

Basic Syntax

wget [options] [URL]

Wget Samples

Downloading with Custom Output Name

wget -O output.txt https://www.example.com/file.txt

Recursively Downloading a Website

wget -r https://www.example.com

wget is a reliable tool for downloading files and web content from the command line. Its simplicity and range of features make it a preferred choice for tasks that involve fetching resources over the Internet.