70 Common Shell Script Interview Questions and Answers

Shell scripting knowledge is essential for system administrators and is frequently tested in Linux job interviews; this guide presents 70 interview‑style questions with clear Bash solutions.

Passing arguments to a script – run a script with ./script argument and access it via $1, $2, etc.

Using parameters inside a script – example copies a file: ./copy.sh file1.txt /tmp/ with script body #!/bin/bash and cp $1 $2.

Counting arguments – $# returns the number of supplied arguments.

Script name and exit status – $0 gives the script name, $? provides the previous command’s exit code, and $? can be used in conditional checks.

File line extraction – get the 10th line with head -10 file | tail -1, the first line with head -1 file, and the last line with tail -1 file.

Loop constructs – Bash supports for, while, and until loops, e.g., for i in $(ls); do echo $i; done or a counting loop while [ $COUNTER -lt 10 ]; do ...; let COUNTER+=1; done.

Conditional tests – numeric comparison uses -gt, -lt, -eq; string comparison uses == inside [[ ... ]]. Example: [[ $string == abc* ]] checks a prefix.

Variable manipulation – length: ${#variable}; substring: ${variable:11:6}; replace: ${variable//pattern/replacement}; remove spaces: echo $string | tr -d " ".

Array handling – define an array: array=("Hi" "my" "name" "is"); access first element ${array[0]}; list all elements ${array[@]}; get indices ${!array[@]}; delete an element unset array[2]; add a new element array[333]="New_element".

Process control – run a command in background with command & or use nohup command & for resilience; redirect output with exec >log.txt 2>&1.

Miscellaneous utilities – count users with wc -l /etc/passwd, list users whose UID is below 100 using awk -F: '$3<100' /etc/passwd, or filter usernames starting with specific prefixes via egrep "^ab|^xy" /etc/passwd | cut -d: -f1.

Overall, the collection equips interviewees with practical Bash snippets for common scripting tasks, from basic syntax to more advanced pattern matching and process management.