Advanced Questions¶
How to use these interview questions
🧠 Read each question carefully.
Try answering it yourself before expanding the answer to compare with the ideal response.
Level: Advanced
🔴 Complex Scenarios & Architecture.
Tackle high-level design, production-grade scaling, security, and advanced internals.
??? question "1. How do you define a function in Bash?"
function_name() {
# commands
}
function keyword:
function function_name {
# commands
}
??? question "2. How do you pass arguments to a function?"
Just like a script: function_name arg1 arg2.
Inside the function, access them using `$1`, `$2`, etc.
??? question "3. How do you return a value from a function?"
Using return exit_code (0-255) or echo for strings.
* `return`: Only returns an integer status code (captured by `$?`).
* `echo`: Prints output which can be captured via substitution `result=$(my_function)`.
??? question "4. What is the scope of variables in a function?" Global by default.
Use the `local` keyword to make a variable restricted to the function:
```bash
local var_name="value"
```
??? question "5. How do you process text using awk?"
awk is used for pattern scanning and processing.
Example: Print the first column of a file:
`awk '{print $1}' file.txt`
??? question "6. How do you replace text using sed?"
sed 's/old/new/g' filename.
* `s`: Substitute
* `g`: Global (replace all occurrences)
??? question "7. How do you find a line number containing a specific string?"
grep -n "string" filename.
??? question "8. How do you handle zombie processes using scripts?"
Find them using ps aux | grep 'Z' and kill the parent process if necessary.
??? question "9. How do you run a script in the background?"
Append & at the end.
Example: `./script.sh &`.
??? question "10. What is nohup?"
No Hang Up.
It allows a command to keep running even after you log out: `nohup ./script.sh &`.
??? question "11. How do you schedule a script to run periodically?"
Using cron.
Edit crontab with `crontab -e` and add entry:
`* * * * * /path/to/script.sh`
??? question "12. How do you check if a port is open?"
nc -zv host port.
Example: `nc -zv localhost 80`.
??? question "13. How do you redirect both stdout and stderr to the same file?"
./script.sh > log.txt 2>&1.
??? question "14. What is eval command?"
It takes arguments and executes them as a command. It creates a "second pass" of parsing.
??? question "15. How do you debug scripts with bash -x?"
It prints each command before executing it, expanding variables. Useful for tracing logic errors.
??? question "16. How do you create a temporary file securely?"
mktemp.
Example: `temp_file=$(mktemp)`.
??? question "17. How do you parse JSON in shell scripts?"
Using jq.
Example: `cat data.json | jq '.key'`.
??? question "18. What is xargs used for?"
To build and execute command lines from standard input.
Example: `find . -name "*.log" | xargs rm`.
??? question "19. How do you check if a variable is empty?"
if [ -z "$var" ]; then ....
??? question "20. How do you get unique lines from a file?"
sort filename | uniq.
🧪 Ready to test yourself?¶
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