Comments

Comments are lines in your shell script that are ignored by the shell. They are used to add notes and explanations to your code for human understanding.

In the shell, a comment starts with a # at the start of a line or after a space. Everything from that # to the end of the line is ignored:

# This is a comment
echo "Hello!"  # This also prints Hello!

When you run the above, only Hello! is printed: the comments are completely invisible to the shell.

A # inside quotes or in the middle of a word does not start a comment: echo "Issue #5" prints Issue #5.

Common uses for comments:

1. Explaining what a command does:

# Print a welcome message
echo "Welcome to the terminal!"

2. Disabling a command temporarily:

# echo "This line is disabled"
echo "This line will execute"

3. The Shebang line:

A special comment at the very top of a shell script tells the system which shell to use:

#!/bin/bash
echo "This script runs with Bash"

This line starts with #! (called a shebang) followed by the path to the shell. It is always the first line of a script.

4. TODO Comments: mark future tasks:

# TODO: Add error handling here
echo "Processing files..."