Shell Script Examples

This page provides a collection of practical shell scripts frequently used in DevOps for automation, system maintenance, and task orchestration.

1. The Foundation: Basic Script

Every shell script should start with a shebang and clear, documented logic.

#!/bin/bash
# Description: My first shell script
 
echo "--- Script Started ---"
echo "Initializing environment..."
echo "Hello, world! Scripting is powerful."

2. Using Variables

Variables make your scripts dynamic and reusable.

#!/bin/bash
 
# Define variables
NAME="John Doe"
ROLE="DevOps Engineer"
SERVER="Web-Server-01"
 
# Access variables
echo "User: $NAME"
echo "Role: $ROLE"
echo "Connected to: $SERVER"

3. Gathering System Information

Scripts are commonly used to pull health metrics from a server.

#!/bin/bash
 
echo "--- System Health Report ---"
echo "Current Date: $(date)"
echo "Host Information: $(whoami) @ $(hostname)"
echo "System Uptime: $(uptime -p)"
echo "Memory Usage:"
free -h | grep "Mem"

4. Interactive Scripts: User Input

Prompting for input makes tools more user-friendly.

#!/bin/bash
 
echo "What is your project name?"
read PROJECT
 
echo "Enter target environment (prod/stage):"
read ENV
 
echo "Setting up $PROJECT for the $ENV environment..."

5. Decision Making: Conditional Logic

Using if-else to handle different outcomes.

#!/bin/bash
 
read -p "Enter server temperature (Celsius): " TEMP
 
if [ "$TEMP" -gt 60 ]; then
    echo "⚠️ ALERT: Server is overheating! Triggering cooling..."
else
    echo "✅ Server temperature is optimal."
fi

6. Batch Automation: For Loops

Loops are essential for performing the same task on multiple items.

#!/bin/bash
 
echo "Creating log backup directories..."
 
for DIR in logs backups reports scripts; do
    echo "Processing: $DIR"
    mkdir -p "/tmp/project/$DIR"
done
 
echo "All directories created in /tmp/project/"

7. Dynamic Strings: Command Substitution

Using the output of one command inside another variable or string.

#!/bin/bash
 
# Count the number of files in the current directory
FILE_COUNT=$(ls -1 | wc -l)
CURRENT_PATH=$(pwd)
 
echo "You are currently in: $CURRENT_PATH"
echo "Total files found: $FILE_COUNT"

[!NOTE] Best Practice: Commenting Notice how each script includes a brief description. Always comment your scripts so your teammates (and "future-you") can understand the logic months later.

Functions & Automation Introduction