CodeToLive

Introduction to Bash Scripting

Bash (Bourne Again SHell) is a Unix shell and command language that is widely used for scripting and automating tasks on Linux and Unix-like systems. It's powerful, flexible, and an essential skill for system administrators and developers.

What is Bash?

Bash is a command processor that typically runs in a text window where the user types commands that cause actions. It can also read and execute commands from files, called shell scripts.

Why Learn Bash?

  • Automation: Automate repetitive tasks
  • System Administration: Manage servers and systems
  • Portability: Works across most Unix-like systems
  • Power: Combine simple commands to perform complex operations

Your First Bash Script

hello_world.sh

#!/bin/bash

# This is a simple bash script
echo "Hello, World!"

How to Run It:

$ chmod +x hello_world.sh
$ ./hello_world.sh
Hello, World!

Script Components

Shebang (#!)

The first line #!/bin/bash is called a shebang. It tells the system which interpreter to use to execute the script.

Comments

Lines starting with # (except the shebang) are comments and are ignored by the interpreter.

echo Command

echo is used to output text to the terminal.

Basic Bash Commands

File Operations


# List files
ls

# Change directory
cd /path/to/directory

# Create directory
mkdir new_directory

# Copy files
cp source.txt destination.txt

# Move/rename files
mv oldname.txt newname.txt

# Remove files
rm file.txt

Text Processing


# View file content
cat file.txt

# Page through file content
less file.txt

# Search in files
grep "pattern" file.txt

# Count lines, words, characters
wc file.txt

System Information


# Show current user
whoami

# Show system information
uname -a

# Show disk usage
df -h

# Show memory usage
free -h

Script Execution Methods

1. Make Executable and Run

$ chmod +x script.sh
$ ./script.sh

2. Pass to Bash Interpreter

$ bash script.sh

3. Source the Script

$ source script.sh

Best Practices

  • Always start with a shebang
  • Use comments to explain complex logic
  • Indent your code for readability
  • Use meaningful variable names
  • Include error handling
  • Test scripts thoroughly

Debugging Bash Scripts

You can debug bash scripts by running them with the -x option:

$ bash -x script.sh

This will print each command before it's executed.

Next Steps

Continue learning with: