Shell scripting is a powerful way to automate tasks and manage system configurations on macOS. This article will guide you through the process of creating and executing shell scripts using the Terminal app on macOS.

What is a Shell Script?

A shell script is a text file containing a sequence of commands for a Unix-based operating system's shell to execute. On macOS, the default shell is Zsh, but you can also use Bash or other shells.

Prerequisites

Before you start, ensure you have access to the Terminal app on your macOS. You can find it in Applications > Utilities > Terminal.

Step-by-Step Guide

1. Create a Shell Script

To create a shell script, you need a text editor. macOS comes with several, including nano, vim, and TextEdit. For this example, we'll use nano.

1. Open Terminal.
2. Type the following command to create a new shell script file:

   nano myscript.sh

3. In the nano editor, type your shell script. Here’s a simple example:

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

4. Save the file by pressing CTRL + X, then Y, and Enter.

2. Make the Script Executable

Before you can run your script, you need to make it executable. Use the chmod command for this purpose:

chmod +x myscript.sh

3. Execute the Shell Script

Now that your script is executable, you can run it from the Terminal:

./myscript.sh

You should see the output:

Hello, World!

Practical Examples

Example 1: Backup Script

Here’s a simple script to back up a directory:

#!/bin/zsh
# Backup script

SOURCE_DIR="$HOME/Documents"
BACKUP_DIR="$HOME/Backup"

# Create the backup directory if it doesn't exist
mkdir -p "$BACKUP_DIR"

# Copy files from source to backup directory
cp -r "$SOURCE_DIR"/* "$BACKUP_DIR"

echo "Backup completed successfully!"

Save this script as backup.sh, make it executable (chmod +x backup.sh), and run it (./backup.sh).

Example 2: System Update Script

This script updates Homebrew and all installed packages:

#!/bin/zsh
# System update script

# Update Homebrew
echo "Updating Homebrew..."
brew update

# Upgrade all installed packages
echo "Upgrading installed packages..."
brew upgrade

echo "System update completed!"

Save this script as update.sh, make it executable (chmod +x update.sh), and run it (./update.sh).

Conclusion

Creating and executing shell scripts on macOS is a straightforward process that can greatly enhance your productivity by automating repetitive tasks. Whether you are backing up files or updating your system, shell scripts provide a versatile toolset.