Shell and Bash Interview Questions: Practical Answers, Commands, and Script Patterns

Originally published on 2010-04-16; fully revised and updated.

This guide converts a legacy shell interview question list into a structured Bash reference for DevOps engineers. It covers essential commands, process control, conditionals and loops, text processing, and safer scripting practices you can use in both interviews and real operations work.

Core shell commands interviewers ask first

These are foundational commands that appear frequently in shell interviews. Knowing both the command and its practical context matters more than memorizing one-liners.

echo "$SHELL"
date
who
pwd
whoami
wc app.log
grep "ERROR" app.log
grep -R "ERROR" /var/log/myappCode language: PHP (php)

Process and job control essentials

Process control questions often test whether you understand inspection first, termination second. Interviewers usually expect safe handling of PIDs and exit status checks.

pid="$(pgrep -f my-service)"
if [ -n "$pid" ]; then
  kill -TERM "$pid"
  sleep 2
  ps -p "$pid"
fiCode language: JavaScript (javascript)

Special shell parameters you should remember

Conditionals, tests, and loops in Bash

Interviewers commonly ask for basic control flow syntax and test operators. Be ready to combine numeric, string, and file checks cleanly.

if/elif with numeric, string, and file tests

count=12
file="/tmp/report.txt"

if [ "$count" -gt 10 ] && [ -f "$file" ]; then
  echo "Large run and report exists"
elif [ -z "$file" ]; then
  echo "No report file specified"
else
  echo "Conditions not met"
fiCode language: PHP (php)

for, while, and case patterns

for env in dev stage prod; do
  echo "Deploying to $env"
done

i=1
while [ "$i" -le 3 ]; do
  echo "Attempt $i"
  i=$((i + 1))
done

read -r action
case "$action" in
  status) ps -ef ;;
  users) who ;;
  now) date ;;
  *) echo "Invalid option" ;;
esacCode language: PHP (php)

Text processing one-liners frequently asked in interviews

grep '^$' file.txt
grep -v '^$' file.txt > no_blanks.txt
sed '/^$/d' file.txt > no_blanks_sed.txt
cut -c 10-20 file.txt
sed -n '25p' file.txt
sed 's/n/xyz/g' file.txt > new_file.txtCode language: JavaScript (javascript)

Legacy reference preserved from the original post: Shell script to read file line by line.

Parsing options with getopts

getopts is a standard way to parse short options like -n 15 -x 20 in shell scripts.

#!/usr/bin/env bash
num=""
xval=""

while getopts "n:x:" opt; do
  case "$opt" in
    n) num="$OPTARG" ;;
    x) xval="$OPTARG" ;;
    *) echo "Usage: $0 -n number -x value"; exit 1 ;;
  esac
done

echo "n=$num x=$xval"Code language: PHP (php)

Quick conceptual answers from common shell interviews

• What is a named pipe? A FIFO special file used for inter-process communication.
• What does cmd1 && cmd2 mean? Run cmd2 only if cmd1 succeeds.
• What does cmd1 || cmd2 mean? Run cmd2 only if cmd1 fails.
• Exported vs non-exported variable: Exported variables are inherited by child processes; non-exported variables remain in the current shell.
• Open a read-only file in vi: vi -R filename.
• Schedule a 4:00 AM daily job: use a cron entry.

crontab -e
0 4 * * * /usr/local/bin/backup.sh

tar -zxvf archive.tar.gz
uname -m
find . -type f -perm 0655 -exec chmod 0755 {} \;Code language: JavaScript (javascript)

Typical script execution workflow

flowchart TD
    A[Run script with arguments] --> B[getopts parses options]
    B --> C[Validate required inputs]
    C --> D{Inputs valid}
    D -- no --> E[Print usage and exit 1]
    D -- yes --> F[Run main commands]
    F --> G[Capture exit code]
    G --> H{Exit code is 0}
    H -- yes --> I[Report success]
    H -- no --> J[Report failure and exit nonzero]

Best practices and common pitfalls

• Prefer safe defaults: inspect with ps/pgrep before using kill.
• Use quoted variables in scripts to avoid word-splitting bugs.
• Treat rm -rf and kill -KILL as last-resort operations.
• Check exit codes ($?) and return nonzero status on failures.
• Use grep -R or find deliberately instead of broad globs like * in large directories.
• Remember that command options and output can vary across Linux/Unix distributions and shells.

If you can explain these commands and patterns clearly, you will handle most shell/Bash interview rounds with confidence.

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

I publish technical articles at DevOps School, travel stories at Holiday Landmark, stock market insights at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow, and SEO and digital marketing strategies at Wizbrand.