1. What are Shell Scripts?

Shell scripts are a way to automate repetitive tasks in Linux. They are text files containing a series of commands that can be executed as a single program.

2. Creating a Simple Shell Script

To create a shell script, save the file with a .sh extension, such as myscript.sh . Start with a shebang line:

#!/bin/bash

Example script for backing up a directory:

#!/bin/bash
# Backup directory
SOURCE="/path/to/source"
DESTINATION="/path/to/backup/$(date +%Y-%m-%d)"
mkdir -p "$DESTINATION"
cp -r "$SOURCE/"* "$DESTINATION/"
echo "Backup completed successfully!"

3. Making the Script Executable

Use the chmod command:

chmod +x myscript.sh

4. Running the Script

You can run the script by typing:

./myscript.sh

5. Using Variables

Shell scripts can use variables to store data:

NAME="John Doe"
echo "Hello, $NAME!"

You can also accept command-line parameters:

echo "Script name: $0"
echo "First argument: $1"

Run it like this:

./myscript.sh argument1

6. Types of Shells

There are several types of shells available, including:

• Bash (Bourne Again Shell): Most widely used shell in Linux.
• Sh (Bourne Shell): The original Unix shell.
• Csh (C Shell): A shell with C-like syntax.
• Fish (Friendly Interactive Shell): A user-friendly shell with advanced features.

7. Common Shell Commands

Here are some commonly used shell commands:

• ls: List directory contents.
• cd: Change the current directory.
• cp: Copy files and directories.
• mv: Move or rename files and directories.
• rm: Remove files or directories.

8. Debugging Shell Scripts

Debugging can help identify issues in your scripts. Use the following options:

• -x: Print commands and their arguments as they are executed.
• -n: Read commands but do not execute them.

Example:

bash -x myscript.sh

9. Error Handling

Error handling is crucial for writing robust scripts. Use the following techniques:

• Check the exit status of commands using $?.
• Use set -e to stop script execution on error.

10. Conclusion

Shell scripting is a powerful tool for automating tasks in Linux. Start with simple scripts and gradually incorporate more complex logic as you gain confidence. Explore the various shell types and choose the one that suits your needs!