Counting lines in a file on Unix/Linux Which single command counts only the number of lines contained in a text file (no words or bytes)?

Introduction / Context:
Simple text analytics are frequently needed on Unix-like systems. The wc (word count) utility quickly provides counts of lines, words, and bytes. Knowing the correct option flags avoids writing custom scripts for basic statistics.

Given Data / Assumptions:

• The input is a regular text file or piped text stream.
• We need the number of lines only.
• We are using a standard POSIX wc implementation.

Concept / Approach:

wc supports independent flags for each metric: -l for lines, -w for words, and -c for bytes. Combining flags prints multiple counts in order. To get lines alone, specify -l by itself.

Step-by-Step Solution:

Verification / Alternative check:

Cross-check with nl -ba filename | tail -n 1, which numbers all lines. The final number should equal the output from wc -l.

Why Other Options Are Wrong:

• wc -c: counts bytes.
• wc -w: counts words.
• wc -r: not a standard option.
• None of the above: incorrect because wc -l is correct.

Common Pitfalls:

Counting lines in files without a trailing newline can yield off-by-one expectations; remember wc -l counts newline characters. On huge files, prefer wc for performance over scripting loops.

Final Answer:

wc -l