30+ Bash Interview Questions And Answers
Bash, also known as Bourne Again Shell, is a command processor that typically runs in a text window, where the user types commands that cause actions. Bash can also read commands from a file, called a script. It is widely used for its ability to process shell commands, use scripts, and automate tasks. Preparing for a Bash interview includes knowing common commands, scripting, and being able to understand and write shell scripts to solve problems. Below are tailored questions and answers for budding Bash users as well as seasoned experts.
Most asked Bash interview questions
Beginners
1.
What is Bash?
1.
What is Bash?
Bash stands for Bourne Again SHell. It's a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell.
2.
How do you execute a Bash script?
2.
How do you execute a Bash script?
You can execute a Bash script by using the command bash script.sh, or by making the script executable with chmod +x script.sh and then running ./script.sh.
3.
How do you store the output of a command in a variable?
3.
How do you store the output of a command in a variable?
You can store the output using command substitution with the following syntax: variable=$(command).
4.
What does the 'echo' command do?
4.
What does the 'echo' command do?
The echo command is used to display a line of text or a variable value to the terminal.
5.
How do you loop through a list of numbers in Bash?
for i in {1..5}; do
echo "Number: $i"
done
5.
How do you loop through a list of numbers in Bash?
for i in {1..5}; do
echo "Number: $i"
done
6.
How can you check if a file exists using Bash?
6.
How can you check if a file exists using Bash?
You can check if a file exists using the test command or the [-f file] expression.
if [ -f "file.txt" ]; then
echo "File exists."
else
echo "File does not exist."
fi
7.
What is a shebang?
7.
What is a shebang?
A shebang (#!) at the start of a script defines the interpreter that should be used to run the file. For Bash scripts, it is usually #!/bin/bash.
8.
How do you comment out a line in Bash?
8.
How do you comment out a line in Bash?
In Bash, you can comment out a line by putting a # at the beginning of the line.
9.
What does the command 'chmod +x filename' do?
9.
What does the command 'chmod +x filename' do?
The command chmod +x filename makes the file called 'filename' executable.
10.
Explain the use of variables in Bash
10.
Explain the use of variables in Bash
In Bash, variables store data that can be used and manipulated throughout the scripts. They aren't typed and can store strings, integers, or the output of commands.
11.
How do you read input during the execution of a script?
11.
How do you read input during the execution of a script?
You can use the read command to take input from the user during script execution.
echo "Enter your name: "
read name
echo "Hello, $name!"
12.
What does 'set -e' do in a script?
12.
What does 'set -e' do in a script?
The command set -e causes a Bash script to exit immediately if a command exits with a non-zero status.
13.
How would you print the last argument of the previous command in Bash?
13.
How would you print the last argument of the previous command in Bash?
Using $_ would print the last argument of the previous command in Bash.
14.
What is the difference between 'echo' and 'printf' in Bash?
14.
What is the difference between 'echo' and 'printf' in Bash?
Echo is a bash builtin command that prints the strings it is being passed as arguments. Printf is more similar to the C printf function, allowing for format specifiers and more precise text formatting.
15.
How do you append text to a file in Bash?
15.
How do you append text to a file in Bash?
You can append text using the '>>' operator. For example, echo "Hello" >> file.txt appends "Hello" to the file 'file.txt'.
Advanced
1.
Explain the use of double brackets [[ ]] in Bash?
1.
Explain the use of double brackets [[ ]] in Bash?
Double brackets [[ ]] are used for advanced conditionals in Bash. They allow for more complex expressions and behave more predictably in corner cases.
2.
What are the benefits of using functions in Bash scripts?
2.
What are the benefits of using functions in Bash scripts?
Functions in Bash scripts allow for code reusability, better organization, and modular scripting. They make complex scripts simpler by splitting the functionality into manageable parts.
3.
How do you send a variable's value from one script to another?
3.
How do you send a variable's value from one script to another?
You can send a variable's value using export to make it available in child scripts or by passing it as an argument.
4.
What does the 'trap' command do?
4.
What does the 'trap' command do?
The trap command in Bash is used to execute a command when the script receives a signal. It's often used to clean up temporary files or reset settings before the script exits.
5.
How do you handle errors in Bash scripts?
5.
How do you handle errors in Bash scripts?
You can handle errors in Bash scripts by using trap, set -e, or by manually checking return values of commands with if or case statements.
6.
In Bash, how can you redirect both stdout and stderr to the same file?
6.
In Bash, how can you redirect both stdout and stderr to the same file?
You can redirect both stdout and stderr using &> operator followed by the filename, like command &> file.
7.
How do you iterate over associative arrays in Bash?
declare -A my_array
code samples to fill here...
7.
How do you iterate over associative arrays in Bash?
declare -A my_array
code samples to fill here...
8.
What is the difference between the 'source' and '.' (dot) command?
8.
What is the difference between the 'source' and '.' (dot) command?
Both the source command and the '.' (dot) execute the content of a file. The difference is only in the syntax. The source is a Bash builtin, and the '.' (dot) is part of POSIX.
9.
Explain what a subshell is?
9.
Explain what a subshell is?
A subshell is a child process launched by a shell or shell script. It has a copy of the shell’s environment and can execute commands in isolation from the parent shell.
10.
How can you execute a command at a given time?
10.
How can you execute a command at a given time?
You can use the at command to schedule a command to be executed at a given time.
11.
How do you create a recursive function in Bash?
function rec_func {
...
rec_func
}
11.
How do you create a recursive function in Bash?
function rec_func {
...
rec_func
}
12.
What does `#!/bin/bash -x` do at the start of scripts?
12.
What does `#!/bin/bash -x` do at the start of scripts?
Having #!/bin/bash -x at the start of bash scripts enables debugging, and it prints each command and its expanded arguments to stderr before execution.
13.
How can you cut a string into parts in Bash?
13.
How can you cut a string into parts in Bash?
You can use parameter expansion or the cut command to split strings into parts in Bash.
my_string="FireHire:HR:Tech"
echo ${my_string//:/ } # outputs: FireHire HR Tech
14.
Explain the process of creating a daemon process in Bash.
14.
Explain the process of creating a daemon process in Bash.
Creating a daemon process in Bash involves setting up a script to run in the background with no controlling terminal, often using `nohup` or `&` and setting appropriate signal handling.
15.
How does `getopts` function help in a Bash script?
15.
How does `getopts` function help in a Bash script?
The `getopts` function helps in parsing command-line arguments and options in a Bash script. It makes handling flags and their values easier and more robust.
Bash Interview Tips
Stay Calm and Composed
Maintaining your composure during an interview is crucial, especially when faced with tough questions. To stay calm, prepare adequately by going through possible questions and how to answer them. Understand that the interviewer is not trying to stump you, but rather gauge your knowledge and problem-solving abilities. Practice breathing techniques and take a moment to pause before responding to gather your thoughts. Remember, it's okay to ask for clarification if a question isn’t clear, ensuring you provide a relevant answer.
Understand the Question
One key to answering tough interview questions, particularly in technical fields like Bash scripting, is to make sure you fully understand what is being asked before you start to answer. Listen carefully, and don’t hesitate to ask the interviewer to repeat or clarify the question. Sometimes, repeating the question in your own words can help ensure that you've grasped the concept. This demonstration of comprehension can be just as important as the answer itself.
Use the STAR Method
The STAR method (Situation, Task, Action, Result) is a structured way of responding to a behavioral-based interview question by discussing the specific situation, task, action, and result of the situation you are describing. Though it's typically used for behavioral questions, it can also be adapted to technical questions. For example, when discussing how you solved a particular scripting challenge, you can explain the Situation you were in, the Task you needed to accomplish, the Actions you took, and the Results of your efforts.
Provide Examples
When answering tough technical questions, providing real-life examples can help the interviewer understand your approach to problem-solving. Discussing past experiences where you successfully utilized Bash scripting to automate tasks or resolve issues can be a powerful demonstration of your skills. If you're asked to dissect a piece of code, walk the interviewer through your thought process as you explain each step. This not only shows your expertise but also gives the interviewer insight into your analytical thinking.
Know Your Resume
Your resume is the basis for many interview questions, so knowing every detail is essential. Be prepared to discuss any of the projects, experiences, or skills listed. If you claim to have expertise in Bash scripting, be ready to talk about specific instances where you've used it, the complexity of the scripts you've written, and the value these scripts have added. Interviewers can often tell when a candidate is embellishing the truth, so ensure that everything on your resume is accurate and that you can discuss each point confidently.
FAQs
Why hire an Bash developer?
Hiring a Bash developer is imperative for efficient scripting and automation in Unix/Linux environments, enhancing the backend performance. Read more: Why hire an Bash developer?
How do I hire Bash developers?
To hire Bash developers, reach out to a trusted partner like FireHire who provides pre-vetted professionals, ensuring a quick and reliable hiring process. Read more: How do I hire Bash developers?
What skills should I look for in an Bash engineer?
A proficient Bash engineer should have strong scripting skills, experience in Unix/Linux environments, and knowledge of command-line tools and server management. Read more: What skills should I look for in an Bash engineer?
Why using FireHire for hiring Bash developers is the best choice?
Choosing FireHire gives you access to highly skilled and vetted Bash developers quickly, with the added benefit of a risk-free hiring process and competitive rates.
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