XK0-006 Automation, Orchestration, and Scripting Practice Question
In a bash script, a variable is set as follows: myvar='Hello World'. Which of the following correctly prints the first 5 characters of the variable?
⚠ Common exam trap
The trap is mixing up prefix/suffix pattern removal (# and %) with substring extraction (:offset:length); candidates often pick ${myvar#?????} thinking # means 'take' rather than 'strip'.
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
✓
echo ${myvar:0:5}
Bash parameter expansion supports substring extraction using the syntax ${variable:offset:length}. With myvar='Hello World', ${myvar:0:5} starts at index 0 and returns 5 characters, yielding 'Hello'. This is the standard, portable way to slice a string in Bash.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
echo ${myvar#?????}
Why it's wrong here
The # operator strips the shortest matching prefix, so ${myvar#?????} removes five characters from the front and prints 'World', not the first five. It is tempting because the five question marks suggest five characters, but substring extraction requires ${myvar:0:5}, which returns 'Hello'.
- ✓
echo ${myvar:0:5}
Why this is correct
Bash substring expansion uses ${parameter:offset:length}, so ${myvar:0:5} extracts five characters starting at index zero, yielding "Hello". The offset is zero-based, and the length is explicit, which is exactly what printing the first five characters requires.
- ✗
echo ${myvar:0-5}
Why it's wrong here
${myvar:0-5} treats the offset as an arithmetic expression evaluating to -5, so bash counts five characters back from the end, printing 'World'. It is tempting because negative offsets do extract trailing characters, but the stem requires the leading five, which needs offset 0 with length 5.
- ✗
echo ${myvar:5}
Why it's wrong here
Substring expansion with a positive offset starts at that index, so ${myvar:5} prints from the sixth character onward, yielding ' World', not the first five. It is tempting because offset syntax does extract substrings, but the correct form needs both offset 0 and length 5.
Go deeper
Related to this question
Key term
Bash script
A Bash script is a text file containing a sequence of commands for the Unix shell Bash, allowing users to automate repetitive tasks and streamline system administration on Linux and macOS.
Key term
Bash
Bash is a command-line interpreter that lets users interact with an operating system by typing text commands instead of clicking icons.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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