Quick Answer
The answer is `for f in *.txt; do`, because this loop structure leverages shell globbing to expand the wildcard `*.txt` into a list of all matching filenames in the current directory, then iterates over each one in turn. This is the standard and most efficient method for a bash loop over files with wildcard patterns, as the shell handles the file matching before the loop even begins, avoiding the need for external commands like `find` or `ls`. On the CompTIA Linux+ XK0-005 exam, this tests your understanding of shell expansion and control structures—a common trap is attempting to use `for f in $(ls *.txt)` or a C-style loop, which can break on filenames with spaces or special characters. Remember the memory tip: "Glob first, loop second"—the wildcard expands before the loop runs, making it both safe and simple.
This XK0-005 practice question tests your understanding of scripting, containers and automation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 needs to iterate over all .txt files in a directory. Which loop structure correctly implements this?
while read line; do
Why wrong: while read is typically used for reading lines from a file, not for iterating over files.
select option; do
Why wrong: select is used to create a menu; it does not iterate over files automatically.
until condition; do
Why wrong: until loops until a condition becomes true; not designed for file iteration.
for f in *.txt; do
This bash loop iterates over each .txt file in the current directory.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
for f in *.txt; do
The `for f in *.txt; do` loop is correct because it uses shell globbing to expand `*.txt` into a list of all .txt filenames in the current directory, then iterates over each filename. This is the standard and most efficient way to process a set of files matching a pattern in Bash and POSIX shell scripting.
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.
while read line; do
Why it's wrong here
while read is typically used for reading lines from a file, not for iterating over files.
select option; do
Why it's wrong here
select is used to create a menu; it does not iterate over files automatically.
until condition; do
Why it's wrong here
until loops until a condition becomes true; not designed for file iteration.
for f in *.txt; do
Why this is correct
This bash loop iterates over each .txt file in the current directory.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates may confuse `while read` (which processes lines of text) with iterating over files, or think `select` is a general-purpose loop, when in fact only `for` with a glob pattern directly matches the requirement of iterating over all .txt files.
Detailed technical explanation
Under the hood, the shell expands `*.txt` into a sorted list of filenames before the loop begins, using pathname expansion (globbing). This expansion respects the current locale's collation order and can be affected by `nullglob` or `failglob` shell options; for example, if no .txt files exist, the loop will execute once with `f='*.txt'` unless `nullglob` is set. In real-world automation, this pattern is preferred over `find` with `while read` because it avoids issues with filenames containing spaces or newlines.
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: for f in *.txt; do — The `for f in *.txt; do` loop is correct because it uses shell globbing to expand `*.txt` into a list of all .txt filenames in the current directory, then iterates over each filename. This is the standard and most efficient way to process a set of files matching a pattern in Bash and POSIX shell scripting.
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
This XK0-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the XK0-005 exam.
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