Master Bash Scripting with Real-World Examples

What is Bash Scripting?

Bash scripting is a powerful way to automate tasks on Unix-like operating systems. Bash (Bourne Again SHell) is the default shell for many Linux distributions and macOS. A Bash script is a plain text file containing a series of commands that the shell executes in sequence.

Whether you're a system administrator, developer, or Linux enthusiast, learning Bash scripting enables you to save time, reduce human error, and increase productivity.

Creating Your First Bash Script

To create a Bash script, follow these steps:

1. Create a new file with a .sh extension.
2. Add the shebang line at the top: #!/bin/bash
3. Write your Bash commands below.
4. Make the script executable using chmod +x script.sh
5. Run it with ./script.sh

#!/bin/bash

echo "Hello, world!"

Variables and User Input

Bash supports variables, both predefined and user-defined. Variables don’t require a data type and are assigned with = without spaces.

#!/bin/bash

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

Reading user input:

#!/bin/bash

echo "Enter your name:"
read username
echo "Welcome, $username!"

Conditionals in Bash

Conditional statements allow your scripts to make decisions. Bash supports if, elif, and else.

#!/bin/bash

num=10
if [ $num -gt 5 ]; then
  echo "Greater than 5"
elif [ $num -eq 5 ]; then
  echo "Equal to 5"
else
  echo "Less than 5"
fi

Loops: Automate Repetition

Loops let you perform tasks multiple times. Bash has for, while, and until loops.

#!/bin/bash

for i in 1 2 3 4 5
do
  echo "Looping ... number $i"
done

#!/bin/bash

count=1
while [ $count -le 5 ]
do
  echo "Count: $count"
  ((count++))
done

Functions in Bash

Functions allow code reuse and organization. Define them before calling.

#!/bin/bash

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

greet "Sublimity Dev Blog"

Practical Examples

Real-world uses of Bash scripts include automation, backups, and system monitoring.

1. Backup Files

#!/bin/bash

tar -czf backup_$(date +%F).tar.gz /home/username/documents

2. Monitor Disk Space

#!/bin/bash

df -h | grep "/dev/sd"

3. User Account Report

#!/bin/bash

cut -d: -f1 /etc/passwd

Debugging and Best Practices

• Use set -x to debug.
• Quote your variables: "$var"
• Always check for command success using $?
• Add comments for maintainability.

#!/bin/bash

set -x  # Start debugging mode
ls /nonexistentdir
set +x  # Stop debugging mode