Explain the diff command.

The diff command is a standard Linux utility used to compare the contents of two files line by line. It highlights the differences between them, making it useful for tasks like code review, version control, and configuration management.

Basic Usage

To use the diff command, you can run:

diff file1.txt file2.txt

Output Explanation

The output format typically includes:

Lines that differ are prefixed with < (from the first file) and > (from the second file).
The output may also show line numbers and change indicators (e.g., c for change, d for delete, a for add).

Example Output

For example, if you compare two files:

1c1
< The quick brown fox jumps over the lazy dog
---
> The quick brown lynx jumps over the lazy dog

This means:

Line 1 in file1.txt needs to be changed to match line 1 in file2.txt.

Useful Options

Side-by-side comparison:
```
diff -y file1.txt file2.txt
```
Unified format (common in patches):
```
diff -u file1.txt file2.txt
```

The diff command is powerful for quickly identifying changes between files. If you have more specific questions or need examples, let me know!