Forem: Basanta Bhusan Khadka

Shell Scripting: Writing and Running Your First Script

Basanta Bhusan Khadka — Tue, 05 Nov 2024 12:23:05 +0000

Prerequisites

Access to a Unix/Linux-based environment (e.g., Ubuntu, macOS, or a Linux VM) and for Windows you could use WSL (Windows Subsystem for Linux) else git bash.
A text editor (like Vim, Nano, or VS Code).
Basic knowledge of using the terminal or command line. (you could refer my blog Shell Scripting: Basic Commands To Just Get You Starting)

Step 1: Create a New Shell Script File

Open the terminal
Navigate to the directory you want to save the script
Use the touch command to create a new file called hello_world.sh

touch hello_world.sh

Step 2: Your First Script
Open the file in your preferred editor(e.g., Vim):

vim hello_world.sh

Your script should start with shebang but if its vim press I to get to insert mode.

#!/bin/bash

The #!/bin/bash line is called a "shebang" and it tells the system to use Bash to run the script in the terminal.

Write a simple echo command to display "Hello, World!" on the terminal:

echo "Hello, World"

Now your script should look like this:

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

Now time to save file since its vim at the moment to save it press Esc, type :wq and press Enter.

Step 3: Make the Script Executable
Before you can run your script you need to give executable permission else it wouldn't be recognized as a program to run. Here's the command:

chmod +x hello_world.sh

This command grants execute (+x) permissions to the file.

Step 4: Run Your Script
Run the script just by typing the command

./hello_world.sh

You should see

Hello, World!

Hurry! Congratulations!! you have just written and executed your first shell script.

Step 5: Practice More

Adding on few tasks for your guys who have been following it all till here:

Write a script to display “Hello, World!” and current date.
It will help you Understand basics of script writing and command execution.
Write a script to print system information like hostname, kernel version and more.
It will help you get comfortable with basic commands and echo statements.
Create a script to display the contents of a directory.
It will help you learn file operations and directory commands.

This guide will help you to write and run your first script and help you enhance your understanding with the tasks to practice to get you up and running and stay motivated.

Shell Scripting: Basic Commands to just get you start scripting

Basanta Bhusan Khadka — Mon, 04 Nov 2024 10:32:58 +0000

Shell scripting is a powerful scripting language that operates within a shell environment, allowing users to automate repetitive tasks, manage files and directories, configure systems, and execute a series of commands in a single script.

Essential Shell Commands: A Practical Guide

Mastering shell commands provides the foundation to harness the power of shell scripting. Here’s a comprehensive guide to the key commands you’ll rely on for efficient file management, system monitoring, text processing, and more.

File and Directory Management

Create a Directory

mkdir new_directory

: Creates a new directory in the current location.

Navigate Directories

cd new_directory

: Changes to the specified directory.

cd ..

: Returns to the previous directory.

List Directory Contents

ls

: Lists files and folders.

ls -l

: Lists detailed information about files (permissions, size, date).

ls -a

: Lists all files, including hidden ones.

Copy Files and Directories

cp source_file.txt destination.txt

: Copies a file to a new location.

cp -r source_directory destination_directory

: Recursively copies an entire directory.

Move or Rename Files

mv oldname.txt newname.txt

: Renames a file.

mv file.txt /path/to/destination/

: Moves a file to a specified directory.

Delete Files and Directories

rm file.txt

: Deletes a file.

rm -r directory/

: Deletes a directory and its contents (use with caution).

File Content Operations
Display File Contents

cat file.txt

: Displays file contents.

head file.txt

: Shows the first 10 lines of a file.

tail file.txt

: Shows the last 10 lines of a file.

Search within Files

grep "search_term" file.txt

: Searches for specific text within a file.

grep -r "search_term" directory/

: Searches within a directory recursively.

Edit a File

vim file.txt

: Opens a file in Vim editor.

nano file.txt

: Opens a file in Nano editor.

File Permissions and Ownership
Set File Permissions

chmod 755 file.txt

: Sets read, write, execute permissions for the owner and read/execute for others.

Change File Ownership

chown user

:group file.txt: Changes file ownership.

System Information and Monitoring
Print Working Directory

pwd

: Shows the current directory path.

Check Disk Usage

df -h

: Displays disk space usage in a human-readable format.

du -h directory/

: Shows the size of a specific directory.

System Information

uname -a

: Provides system information.

top

: Real-time process monitor.

ps -ef

: Lists running processes.

Network and Connectivity Commands
Network Connectivity Check

ping example.com

: Checks if a host is reachable.

View Network Configuration

ifconfig

: Displays network interfaces (use ip a on newer systems).

Compression and Archiving
Create Archives

tar -cvf archive.tar directory/

: Creates a tar archive.

tar -czvf archive.tar.gz directory/

: Creates a compressed (gzip) tar archive.

Extract Archives

tar -xvf archive.tar

: Extracts a tar archive.

tar -xzvf archive.tar.gz

: Extracts a gzip-compressed tar archive.

Advanced Utilities
Output Redirection

command > output.txt

: Redirects output to a file (overwrites).

command >> output.txt

: Appends output to a file.

Command Chaining and Piping

ls -l | grep "search_term"

: Pipes output of one command into another.

Set Environment Variables

export VAR_NAME="value"

: Sets an environment variable.

Command History

history

: Displays command history.

With these essential commands, you’re well-equipped to start scripting effectively in the shell environment. Mastering these commands opens up the potential for automation, efficient file handling, and streamlined system administration through shell scripting.