This XK0-005 practice question tests your understanding of scripting, containers and automation. 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 systems administrator creates a bash script that processes log files. The script uses a for loop to iterate over files in /var/log and runs a command on each. Which of the following would prevent the script from failing if no files match the pattern?
set -u
Why wrong: Exits on unset variable, not glob issue.
set -e
Why wrong: Exits script on any error, doesn't handle empty glob.
shopt -s failglob
Why wrong: Causes script to error if no match.
shopt -s nullglob
Expands to nothing, preventing failure.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
shopt -s nullglob
Option D is correct because `shopt -s nullglob` causes the shell to expand a glob pattern that matches no files into an empty string rather than leaving the pattern literal. Without this setting, if no files match the pattern in `/var/log`, the for loop receives the literal pattern string (e.g., `*.log`) and attempts to process it as a filename, which would cause the command to fail or produce unexpected results. Enabling nullglob ensures the loop body simply does not execute when no matches exist, preventing script failure.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
set -u
Why it's wrong here
Exits on unset variable, not glob issue.
set -e
Why it's wrong here
Exits script on any error, doesn't handle empty glob.
shopt -s failglob
Why it's wrong here
Causes script to error if no match.
shopt -s nullglob
Why this is correct
Expands to nothing, preventing failure.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse `nullglob` with `failglob` or assume that `set -e` or `set -u` can handle glob failures, when in fact only `nullglob` prevents the literal pattern string from being passed as an argument, thereby avoiding a command failure.
Detailed technical explanation
Under the hood, when a glob pattern like `/var/log/*.log` matches no files, Bash by default leaves the pattern unchanged and passes it as a literal argument to the command. The `nullglob` shell option (enabled via `shopt -s nullglob`) alters this behavior by removing the pattern entirely from the argument list, effectively making the loop iterate over zero items. This is particularly important in scripts that process log files or other variable sets of files, where the absence of matching files should be handled gracefully without special conditional checks.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Scripting, Containers and Automation — This question tests Scripting, Containers and Automation — Read the scenario before looking for a memorised answer..
The correct answer is: shopt -s nullglob — Option D is correct because `shopt -s nullglob` causes the shell to expand a glob pattern that matches no files into an empty string rather than leaving the pattern literal. Without this setting, if no files match the pattern in `/var/log`, the for loop receives the literal pattern string (e.g., `*.log`) and attempts to process it as a filename, which would cause the command to fail or produce unexpected results. Enabling nullglob ensures the loop body simply does not execute when no matches exist, preventing script failure.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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