Which command can you execute to count only the number of lines in a file on Unix/Linux?

Introduction / Context:
Counting lines is a frequent need when validating datasets, logs, or configuration files. Unix/Linux provides a compact utility that can report multiple metrics, and with the right switch it outputs exactly the line count, making it convenient for scripting and quick checks.

Given Data / Assumptions:

• You have a text file and want the total number of lines.
• Only standard POSIX tools are assumed.
• Output format should be script-friendly if needed.

Concept / Approach:
The 'wc' (word count) utility prints lines, words, and bytes. By passing the '-l' option, 'wc' restricts output to the line count. You can supply one or more filenames; with multiple files, it prints per-file counts plus a total. In pipelines, 'wc -l' counts the number of input lines from standard input.

Step-by-Step Solution:

Verification / Alternative check:
Use 'awk 'END{print NR}' filename' or 'nl -ba filename | tail -n 1' to confirm the same count. For binary or huge files, ensure the input has newline-terminated records to avoid off-by-one expectations.

Why Other Options Are Wrong:

• lc / cl / count: Not standard Unix commands.
• None of the above: Incorrect because 'wc -l' is the exact tool for line counts.

Common Pitfalls:
Assuming bytes equal characters in multi-byte encodings (irrelevant for line counts) and forgetting input redirection when you do not want the filename echoed with the count.

Final Answer:
wc -l