50 cool Bash scripts! and what they do …

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12 Mar 2024

Hey there! So, you’ve heard of Bash before, right? It’s like the “cool kid” of the command-line world, somewhat akin to the Windows Command Prompt (CMD), but with a twist. If you’re nodding along but haven’t really delved into it, you’re in for a treat!
Think of Bash as your trusty sidekick for navigating and controlling your computer via text commands. It’s used by virtually every major tech company and system developers worldwide. You see, the magic of Bash lies in its simplicity and efficiency. With just a few well-placed keystrokes, you can zip through tasks, manage files, and automate processes much faster than clicking around with a mouse and a graphical user interface (GUI).
Even if you’re on a Windows machine, fear not! You can tap into the power of Bash through Windows Subsystem for Linux (WSL), and suddenly, you’ll find yourself effortlessly conquering tasks that used to feel daunting. So, if you’ve been hesitating, it’s time to dive in and discover how Bash can supercharge your computing experience. Trust me, it’s worth it!
That said, Here’s a list of 50 common Bash scripts along with explanations of their use that you could try since we learn by doing:
Hello World:

#!/bin/bash
echo "Hello, World!"

Explanation: A basic script that prints “Hello, World!” to the terminal.
File Backup

#!/bin/bash
source_dir="/path/to/source"
backup_dir="/path/to/backup"
timestamp=$(date +%Y%m%d%H%M%S)
backup_file="backup_$timestamp.tar.gz"
tar -czvf "$backup_dir/$backup_file" "$source_dir"

Explanation: Creates a timestamped backup of a directory using tar compression.
Directory Listing

#!/bin/bash
ls -l

Explanation: Lists files and directories in the current directory with details.
File Count

#!/bin/bash
file_count=$(ls | wc -l)
echo "Number of files: $file_count"

Explanation: Counts the number of files in the current directory.
Disk Usage

#!/bin/bash
df -h

Explanation: Displays disk usage information.
System Info

#!/bin/bash
uname -a

Explanation: Prints system information, including the kernel version
File Rename

#!/bin/bash
old_name="old.txt"
new_name="new.txt"
mv "$old_name" "$new_name"

Explanation: Renames a file from “old.txt” to “new.txt.”
File Permissions

#!/bin/bash
file="file.txt"
chmod +x "$file"

Explanation: Grants execute permission to a file.
User Info

#!/bin/bash
username=$(whoami)
echo "Current user: $username"

Explanation: Prints the username of the current user.
Process List

#!/bin/bash
ps aux

Explanation: Lists all running processes.
Process Kill

#!/bin/bash
process_id=12345
kill -9 "$process_id"

Explanation: Kills a process by its process ID.
Check Internet Connection

#!/bin/bash
ping -c 5 google.com

Explanation: Checks internet connectivity by pinging Google.
Disk Cleanup

#!/bin/bash
du -sh /var/log/*
rm -rf /var/log/*

Explanation: Displays disk usage of log files and then deletes them
System Shutdown

#!/bin/bash
shutdown -h now

Explanation: Shuts down the system immediately.
System Reboot

#!/bin/bash
reboot

Explanation: Reboots the system.
File Search

#!/bin/bash
search_dir="/path/to/search"
search_term="pattern"
grep -r "$search_term" "$search_dir"

Explanation: Searches for a specified pattern recursively in files.
Disk Space Alert

#!/bin/bash
threshold=90
current_usage=$(df -h / | awk 'NR==2 {print $5}' | tr -d '%')
if [ "$current_usage" -ge "$threshold" ]; then
    echo "Disk space is running low!"
else
    echo "Disk space is okay."
fi

Explanation: Monitors disk space usage and provides an alert if it exceeds a specified threshold.
Check Service Status

#!/bin/bash
service_name="nginx"
if systemctl is-active --quiet "$service_name"; then
    echo "$service_name is running."
else
    echo "$service_name is not running."
fi

Explanation: Checks if a system service is running.
System Backup Script

#!/bin/bash
source_dir="/path/to/source"
backup_dir="/path/to/backup"
timestamp=$(date +%Y%m%d%H%M%S)
backup_file="backup_$timestamp.tar.gz"
tar -czvf "$backup_dir/$backup_file" "$source_dir"

Explanation: Creates a timestamped backup of a directory, similar to the intermediate script but without user prompts.
Log Rotation

#!/bin/bash
log_file="/path/to/logfile.log"
max_log_size=10M
if [ -f "$log_file" ]; then
    current_size=$(du -b "$log_file" | awk '{print $1}')
    if [ "$current_size" -ge "$max_log_size" ]; then
        mv "$log_file" "$log_file.old"
        touch "$log_file"
    fi
fi

Explanation: Rotates log files by renaming them when they reach a specified size.
User Management

#!/bin/bash
username="newuser"
password="password123"
useradd "$username"
echo "$username:$password" | chpasswd

Explanation: Creates a new user and sets their password.
File Encryption

#!/bin/bash
file_to_encrypt="file.txt"
gpg -c "$file_to_encrypt"

Explanation: Encrypts a file using GPG.
File Decryption

#!/bin/bash
encrypted_file="file.txt.gpg"
gpg -d "$encrypted_file" > "decrypted_file.txt"

Explanation: Decrypts an encrypted file.
File Compression

#!/bin/bash
compressed_file="compressed_file.tar.gz"
tar -xzvf "$compressed_file"

Explanation: Compresses a file using tar and gzip.
File Decompression

#!/bin/bash
compressed_file="compressed_file.tar.gz"
tar -xzvf "$compressed_file"

Explanation: Decompresses a file compressed with tar and gzip.
CSV File Processing

#!/bin/bash
input_csv="data.csv"
output_file="output.txt"
awk -F ',' '{print $1,$2}' "$input_csv" > "$output_file"

Explanation: Extracts specific columns from a CSV file and saves them to a new file.
Log Analysis

#!/bin/bash
log_file="access.log"
unique_ips=$(awk '{print $1}' "$log_file" | sort -u | wc -l)
error_count=$(grep -c 'ERROR' "$log_file")
echo "Unique IPs: $unique_ips"
echo "Total Errors: $error_count"

Explanation: Analyzes an access log file, counting unique IP addresses and error occurrences.
Send Email Alert

#!/bin/bash
email="user@example.com"
subject="Alert"
message="Disk space is running low!"
echo "$message" | mail -s "$subject" "$email"

Explanation: Sends an email alert.
Database Backup

#!/bin/bash
db_name="mydb"
backup_file="backup.sql"
mysqldump -u username -p$password "$db_name" > "$backup_file"

Explanation: Creates a MySQL database backup.
SSH Key Generation

#!/bin/bash
ssh-keygen -t rsa -b 4096 -f ~/.ssh/mykey

Explanation: Generates an SSH key pair.
SSH Key Copy

#!/bin/bash
ssh-copy-id user@hostname

Explanation: Copies an SSH public key to a remote server for passwordless login.
File Comparison

#!/bin/bash
file1="file1.txt"
file2="file2.txt"
if cmp -s "$file1" "$file2"; then
    echo "Files are identical."
else
    echo "Files are different."
fi

Explanation: Compares two files to check if they are identical.
Cron Job Example

#!/bin/bash
backup_dir="/path/to/backup"
timestamp=$(date +%Y%m%d%H%M%S)
backup_file="backup_$timestamp.tar.gz"
tar -czvf "$backup_dir/$backup_file" /path/to/source

Explanation: A script that can be scheduled as a cron job to automate backups at regular intervals.
Folder Synchronization

#!/bin/bash
source_dir="/path/to/source"
destination_dir="/path/to/destination"
rsync -av "$source_dir/" "$destination_dir/"

Explanation: Synchronizes the contents of two directories using rsync.
URL Download

#!/bin/bash
url="https://example.com/file.txt"
output_file="downloaded_file.txt"
wget "$url" -O "$output_file"

Explanation: Downloads a file from a URL using wget.
Input Validation

#!/bin/bash
read -p "Enter a number: " number
if [[ ! "$number" =~ ^[0-9]+$ ]]; then
    echo "Invalid input. Please enter a number."
else
    echo "You entered: $number"
fi

Explanation: Validates user input to ensure it is a number.
String Manipulation

#!/bin/bash
string="Hello, World!"
uppercase_string=$(echo "$string" | tr '[:lower:]' '[:upper:]')
echo "$uppercase_string"

Explanation: Converts a string to uppercase.
File Watcher

#!/bin/bash
directory="/path/to/watch"
inotifywait -m -r -e create,modify,delete "$directory" |
while read path action file; do
    echo "File $file was $action."
done

Explanation: Watches a directory for file changes using inotifywait.
JSON Parsing

#!/bin/bash
json_string='{"name": "John", "age": 30}'
name=$(echo "$json_string" | jq -r '.name')
age=$(echo "$json_string" | jq -r '.age')
echo "Name: $name, Age: $age"

Explanation: Parses JSON data and extracts specific fields using jq.
Zip File Compression

#!/bin/bash
file_to_compress="file.txt"
zip "compressed_file.zip" "$file_to_compress"

Explanation: Compresses a file using ZIP compression.
Zip File Extraction

#!/bin/bash
zip_file="compressed_file.zip"
unzip "$zip_file"

Explanation: Extracts files from a ZIP archive.
PDF Conversion

#!/bin/bash
input_file="document.docx"
output_file="document.pdf"
libreoffice --headless --convert-to pdf "$input_file"

Explanation: Converts a document to PDF using LibreOffice.
CSV to Excel

#!/bin/bash
input_csv="data.csv"
output_xlsx="data.xlsx"
ssconvert "$input_csv" "$output_xlsx"

Explanation: Converts a CSV file to an Excel (XLSX) file using Gnumeric’s ss convert.
File Splitting

#!/bin/bash
input_file="large_file.txt"
split -b 1M "$input_file" "split_file"

Explanation: Joins split files to reconstruct the original file.
File Joining

#!/bin/bash
cat split_file* > "large_file.txt"

Explanation: Joins split files to reconstruct the original file.
IP Address Validation

#!/bin/bash
read -p "Enter an IP address: " ip_address
if [[ $ip_address =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
    echo "Valid IP address: $ip_address"
else
    echo "Invalid IP address."
fi

Explanation: Validates user input as an IP address.
URL Validation

#!/bin/bash
read -p "Enter a URL: " url
if [[ $url =~ ^(http|https)://[A-Za-z0-9.-/]+$ ]]; then
    echo "Valid URL: $url"
else
    echo "Invalid URL."
fi

Explanation: Validates user input as a URL.
File Permissions Report

#!/bin/bash
find /path/to/files -type f -exec ls -l {} \; > permissions_report.txt

Explanation: Creates a report of file permissions for all files in a directory
Password Generator

#!/bin/bash
length=12
characters="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*()"
password=$(head /dev/urandom | tr -dc "$characters" | head -c "$length")
echo "Generated Password: $password"

Explanation: Generates a random password of specified length using characters from a set.
These scripts cover a wide range of common tasks in Bash scripting, from basic file operations to more advanced tasks like JSON parsing and PDF conversion. Beginners can start with the simpler scripts and gradually move on to more complex ones as they gain familiarity with Bash.