Mastering Intermediate Shell Scripting Interview Questions

Shell scripting allows automation of repetitive tasks and can optimize workflow efficiencies. As such recruiters often test candidates on intermediate shell scripting concepts during technical interviews. Preparing for such questions is key to highlighting your skills and landing the role. This comprehensive guide covers some of the most common and critical intermediate-level shell scripting interview questions you should expect.

Discussing Shell Scripting Drawbacks

Interviewers commonly ask candidates to reflect critically on technologies, Be ready to discuss disadvantages of shell scripting such as

• Portability issues: Shell scripts rely heavily on Bash or other shells. Variations across shells can cause portability problems.

• Difficult debugging: Shell scripts lack robust debugging tools like IDEs offer for compiled languages. Debugging relies on basic techniques like echo statements.

• Limited capabilities: Shells have restricted capabilities compared to high-level languages. Complex programs involving heavy computation, GUIs, etc. are better handled by Python, Java, etc.

• Security vulnerabilities: Scripts can have vulnerabilities if input validation isn’t done properly. Shells provide many low-level commands that can be exploited if used carelessly.

Discussing cons alongside pros shows you can take a measured approach and have deep understanding of technologies.

Explaining GUI Scripting

Many roles require building user interfaces and automation. Interviewers may ask questions like:

• What is GUI scripting?

• How is it different from shell scripting?

• What tools can be used for GUI scripting on Linux?

Highlight that GUI scripting focuses on automating interactions with graphic interfaces, not just the command line. Tools like AutoIt and PyAutoGUI allow simulating mouse clicks, keyboard inputs, etc. to control GUI apps. Mention advantages like cross-platform support and integration with scripts.

Using Special Variables Like $#

Familiarity with special variables is imperative. Be prepared for questions about:

• What does $# signify in shell scripts?

• What use cases is it helpful for?

• Provide an example of using $# in a script.

Explain that $# returns the number of arguments passed to a script or function. Use cases include:

• Checking correct number of args are passed
• Iterating through each arg with a loop
• Creating usage info/help text based on args needed

An example is:

if [ $# -ne 2 ]; then  echo "Usage: ${0} <arg1> <arg2>"  exit 1fi

This validates 2 args are passed before execution.

Recognizing Standard Streams

You should be able to identify standard I/O streams:

• What are the standard streams in Linux?

• Which file descriptors do they correspond to?

• What are some common ways to use them in shell scripts?

Cover how stdin (0), stdout (1), and stderr (2) represent input, output, and error streams. Give examples like redirecting stdout/stderr to files, piping stdout to other commands, reading stdin via echoes or read commands.

Explaining Cron Jobs

Automation often relies on cron. Prepare for cron questions:

• What is crontab in Linux?

• How would you schedule cron jobs?

• What are important considerations when running cron jobs?

Discuss how crontab configures scheduled tasks. Explain how to use crontab syntax to set schedules. Highlight tips like setting appropriate environments, logging output, avoiding overlaps, etc. when managing multiple cron jobs.

Differentiating $@ and $*

Be ready to compare special parameters $@ and $*:

• What is the difference between $@ and $* in shell scripts?

• When would you use one versus the other?

• Provide an example demonstrating their differences.

Explain that $* treats arguments as a single string while $@ treats them separately. Use $* for a collective group of args and $@ when needing to process args distinctly. An example is:

for arg in "$@"do  echo "$arg" done

This iterates through each arg individually.

Preparing explanations for questions like these will help you master key intermediate shell scripting topics. With practice, you’ll be able to highlight both your breadth and depth of knowledge during the interview.