Shell pipelines and counting: Using standard pipelines, which command counts the number of directory entries shown by ls in the current directory (one count per line of ls output)?

Introduction / Context:
Pipelines combine simple UNIX tools to accomplish useful tasks. A common need is to count how many items a command lists. The wc (word count) utility can report lines, words, and bytes for its input, making it perfect to summarize ls output.

Given Data / Assumptions:

• The goal is to count entries printed by ls in the current directory.
• No need to handle hidden files unless you add -a to ls.
• Default ls output prints one entry per line (depending on aliases and terminal width).

Concept / Approach:

wc -l counts lines of input. Piping ls to wc -l yields the number of lines produced by ls, which typically corresponds to the number of visible directory entries. If your environment formats ls in multiple columns, use ls -1 to force one per line before piping.

Step-by-Step Solution:

Verification / Alternative check:

Compare ls -1 output visually and ensure the number of lines matches wc -l. For robust scripting, prefer find with explicit type filters and null-delimited results when filenames include newlines.

Why Other Options Are Wrong:

a: wc -c reports byte count, not lines.

b: wc -w reports word count, not reliable for filenames with spaces.

d: wc without options prints lines, words, and bytes; it does not directly return just the line count.

e: Not applicable because ls | wc -l is correct.

Common Pitfalls:

Relying on ls default column formatting; to be safe, use -1. Also note that ls counts directories and files together; use find to tailor results precisely.

Final Answer:

ls | wc -l