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Correct Usage: wc -l

The command:

Explanation:

• wc stands for “word count”.

• The -l option counts the number of lines in the specified file.

• It returns a number representing total lines, followed by the file name.

Example:

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Why Other Options Are Incorrect:

• A. pc – f: Not a valid Unix command.

• B. ls –a: Lists all files including hidden ones in a directory; does not count lines.

• C. df –h: Displays disk space usage in a human-readable format; unrelated to line counts.

• D. wc –I: Incorrect option; -I is not a standard flag for wc.

Note: The option should be lowercase -l, not an uppercase “i” or “L”.

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Conclusion

To count the number of lines in a file on Unix/Linux systems, use wc -l. It’s simple, efficient, and widely used by system admins and developers alike.

Correct Answer: D. wc -l (not wc -I as in the question, which appears to be a typo)

Let me know if you’d like a cheat sheet on commonly used Unix commands.