Quick Answer
The answer is carriage return characters (\r) hidden in the script, which cause the shebang line to be read as /bin/bash\r, a path that does not exist on Linux. This happens because Windows uses CRLF line endings, while Linux expects only LF; when the script is transferred without conversion, the \r character remains attached to the interpreter path, producing a “No such file or directory” error even though permissions and the shebang appear correct. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of cross-platform file encoding issues—a common trap where examinees overlook invisible characters and instead blame permissions or the shebang syntax. A quick fix is to run `dos2unix script.sh` or use `sed -i 's/\r$//' script.sh` to strip the carriage returns. Memory tip: think “CRLF = Carriage Return, Linux Fails”—if your script was edited on Windows, always convert line endings first.
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 senior administrator is troubleshooting a shell script that fails to execute properly. The script starts with #!/bin/bash and has execute permissions. Which of the following could cause the script to fail to run when invoked as ./script.sh?
The shebang line is not on the first line.
Why wrong: Shebang must be first line, but that would cause an error.
The script contains carriage return characters (\r).
Can cause 'No such file or directory'.
The script uses #!/bin/sh instead of bash.
Why wrong: That is a valid shebang.
The script starts with a byte order mark (BOM).
Why wrong: BOM is valid in UTF-8 scripts.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The script contains carriage return characters (\r).
Option B is correct because carriage return characters (\r) are a common issue when scripts are edited on Windows and then transferred to Linux. The shebang line #!/bin/bash expects a Unix-style line ending (LF), but \r characters cause the shell to interpret the command interpreter as '/bin/bash\r', which is not a valid executable path. This results in a 'No such file or directory' error when the script is invoked as ./script.sh, even though permissions are correct.
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.
The shebang line is not on the first line.
Why it's wrong here
Shebang must be first line, but that would cause an error.
The script contains carriage return characters (\r).
Why this is correct
Can cause 'No such file or directory'.
Related concept
Read the scenario before looking for a memorised answer.
The script uses #!/bin/sh instead of bash.
Why it's wrong here
That is a valid shebang.
The script starts with a byte order mark (BOM).
Why it's wrong here
BOM is valid in UTF-8 scripts.
Common exam traps
The trap here is that candidates may think the shebang line must be on the first line (Option A) is the issue, but Cisco tests the subtle Windows line-ending problem (\r) that causes the interpreter path to be invalid, which is a common real-world pitfall when scripts are edited in Windows environments and transferred to Linux.
Detailed technical explanation
Under the hood, the Linux kernel's binfmt_script handler reads the first two bytes of the file to detect the shebang (#!) and then parses the interpreter path until the first newline (LF, 0x0A). Carriage return characters (\r, 0x0D) are not stripped, so the path becomes '/bin/bash\r', which fails because the filesystem does not contain a file named '/bin/bash\r'. In real-world scenarios, this often manifests as a cryptic error like './script.sh: line 1: /bin/bash\r: No such file or directory', which can be diagnosed with 'cat -v script.sh' or 'od -c script.sh' to reveal the \r characters.
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: The script contains carriage return characters (\r). — Option B is correct because carriage return characters (\r) are a common issue when scripts are edited on Windows and then transferred to Linux. The shebang line #!/bin/bash expects a Unix-style line ending (LF), but \r characters cause the shell to interpret the command interpreter as '/bin/bash\r', which is not a valid executable path. This results in a 'No such file or directory' error when the script is invoked as ./script.sh, even though permissions are correct.
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 11, 2026
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