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Shell Scripting Interview Questions

Automation is key in Linux administration. Shell scripting questions test your ability to automate tasks efficiently.

Core Questions​

1. What is a Shebang (#!)?​

The shebang is the first line of a script that specifies the interpreter to execute the file. Example: #!/bin/bash tells the system to use the Bash shell.

2. How do you handle command-line arguments?​

Arguments are accessed using positional parameters:

  • $0 - Name of the script
  • $1, $2, etc. - First, second arguments
  • $# - Number of arguments passed
  • $@ - All arguments as a list

3. Explain the difference between $? and $$.​

  • $? - Returns the exit status of the last executed command (0 usually means success, non-zero means failure).
  • $$ - Returns the Process ID (PID) of the current shell.

Practical Examples​

Basic Conditional Statement:

#!/bin/bash
if [ -f "/etc/passwd" ]; then
    echo "File exists."
else
    echo "File does not exist."
fi

Looping through files:

for file in *.txt; do
    echo "Processing $file"
done

Best Practices​

  • Error Handling: Always mention checking $? after critical commands or using set -e at the top of scripts to exit on error.
  • Quoting: Stress the importance of double-quoting variables (e.g., "$VAR") to prevent word splitting and globbing issues.