- A
lines contains a string including the filename, not just a number.
wc -l outputs 'number filename', so lines is not a pure integer.
- B
wc -l requires the -c option to count correctly.
Why wrong: wc -l counts lines, -c counts characters.
- C
The script has a syntax error in the echo command.
Why wrong: The syntax is valid; the problem is semantic.
- D
$((...)) cannot read a variable from command substitution.
Why wrong: $((...)) works with variables; the issue is that lines is not numeric.
Question 201 of 537
wc -l Output: Filename Included Causes Arithmetic Error
This EX200 practice question tests your understanding of create simple shell scripts. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A script contains: lines=$(wc -l /etc/passwd); echo $((lines+1)). The output is unexpected. What is the problem?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
lines contains a string including the filename, not just a number.
The command substitution `$(wc -l /etc/passwd)` outputs the line count followed by a space and the filename `/etc/passwd`. This entire string (e.g., `35 /etc/passwd`) is stored in the variable `lines`. When `$((lines+1))` attempts arithmetic expansion, it fails because the string is not a pure integer, causing the shell to treat it as 0 or produce an error, resulting in an unexpected output.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
lines contains a string including the filename, not just a number.
Why this is correct
wc -l outputs 'number filename', so lines is not a pure integer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
wc -l requires the -c option to count correctly.
Why it's wrong here
wc -l counts lines, -c counts characters.
- ✗
The script has a syntax error in the echo command.
Why it's wrong here
The syntax is valid; the problem is semantic.
- ✗
$((...)) cannot read a variable from command substitution.
Why it's wrong here
$((...)) works with variables; the issue is that lines is not numeric.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Red Hat often tests the candidate's understanding that `wc` includes the filename in its output when given a file argument, and that arithmetic expansion requires a pure numeric string, causing candidates to overlook the need to strip the filename or use input redirection.
Detailed technical explanation
How to think about this question
By default, `wc` outputs the count followed by the filename when a file argument is given. To suppress the filename, you must redirect input (e.g., `wc -l < /etc/passwd`) or use `cut`/`awk` to extract only the number. The arithmetic expansion `$((...))` in Bash performs integer arithmetic and will coerce non-numeric strings to 0, leading to silent errors. In real-world scripting, this is a common pitfall when parsing command output without stripping unwanted text.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the EX200 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this EX200 question test?
Create simple shell scripts — This question tests Create simple shell scripts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: lines contains a string including the filename, not just a number. — The command substitution `$(wc -l /etc/passwd)` outputs the line count followed by a space and the filename `/etc/passwd`. This entire string (e.g., `35 /etc/passwd`) is stored in the variable `lines`. When `$((lines+1))` attempts arithmetic expansion, it fails because the string is not a pure integer, causing the shell to treat it as 0 or produce an error, resulting in an unexpected output.
What should I do if I get this EX200 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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