Which of the following UNIX/Linux pipes will count the number of lines in all…

Correct command: cat *.[ch] | wc -l

Why this works:

• The glob pattern *.[ch] matches files whose names end with .c or .h.

• cat concatenates the contents of those files and writes them to standard output.

• wc -l reads the input and counts the number of newline characters, giving the total number of lines.

Common mistakes to avoid:

• Using [c-h] creates a character range (c through h) rather than matching the two extensions .c and .h. Use [ch] to list the two characters explicitly.

• Confusing the digit '1' with the letter 'l' in the wc flag. The correct flag to count lines is -l (lowercase L).

• Piping to ls -1 lists filenames instead of counting lines — use wc -l to count lines.

Alternative:

• wc -l *.[ch] will print the line count for each matching file and a total. If you only want the combined total as a single number, use cat *.[ch] | wc -l.