Linux Shell Scripting Quiz Challenge | Linux Shell Scripting Interview questions and answers

Shell Scripting Challenge - Bash & Automation

💻 Linux Shell Scripting Challenge

Test your knowledge of Bash syntax, control structures, and essential scripting commands. **Pass with 80% to proceed to the next difficulty level.**

Syntax & Variables: 0/10 (0%)

Control Flow: 0/10 (0%)

Functions & Advanced: 0/10 (0%)

Level 1: Basic Syntax and Variables

1.1 What is the correct "shebang" line to start a script that uses the Bash shell?

A. `#!/usr/bin/shell` B. `#!/bin/bash` C. `//bin/bash`

**Correct Answer: B. `#!/bin/bash`**. The **shebang** line is `#!` followed by the absolute path to the interpreter (Bash).

1.2 How do you correctly assign the string "Hello World" to a variable named `GREETING` in Bash?

A. `GREETING = "Hello World"` B. `GREETING="Hello World"` C. `$GREETING = "Hello World"`

**Correct Answer: B.** In Bash variable assignment, there must be **no spaces** around the `=` sign.

1.3 Which syntax is used to access or reference the value of a variable named `PATH`?

A. `PATH` B. `$PATH` C. `%PATH%`

**Correct Answer: B. `$PATH`**. The dollar sign (`$`) is used for **variable expansion**, retrieving the value stored in the variable.

1.4 What is the purpose of the `chmod +x myscript.sh` command?

A. It executes the script immediately. B. It grants execute permission to the script file. C. It compiles the script into a binary executable.

**Correct Answer: B.** The `+x` option adds the **execute** permission, which is necessary to run the script directly as `./myscript.sh`.

1.5 Which special variable holds the exit status (return code) of the most recently executed command?

A. `$0` B. `$@` C. `$?`

**Correct Answer: C. `$?`**. An exit status of **0** typically means success, and any non-zero value indicates an error.

1.6 How do you access the second argument passed to a shell script?

A. `$2` B. `$1` C. `$2`

**Correct Answer: A. `$2`**. Command-line arguments are accessed sequentially as `$1`, `$2`, `$3`, etc. (`$0` is the script's name).

1.7 In a shell script, what is the best practice for reading user input and storing it in a variable named `USER_INPUT`?

A. `read -p "Enter value: " USER_INPUT` B. `echo "Enter value: " > USER_INPUT` C. `input USER_INPUT`

**Correct Answer: A.** The **`read`** command is used to read input from the standard input (keyboard), and the `-p` flag displays a prompt.

1.8 What is the command substitution syntax used to execute a command and capture its output into a variable?

A. `VAR=`ls -l`` B. `VAR=$(ls -l)` C. `VAR={ls -l}`

**Correct Answer: B. `VAR=$(ls -l)`**. The `$()` syntax is the modern, preferred way for **command substitution**. (The backtick syntax is deprecated).

1.9 Which statement is generally true about using double quotes (`" "`) around variable expansions?

A. They prevent all variable expansion. B. They preserve spaces and newline characters in the variable's value. C. They are only needed when using the `echo` command.

**Correct Answer: B.** Double quotes prevent word splitting and globbing, ensuring the variable's content, including spaces, is treated as a single argument.

1.10 What character is typically used in Bash to denote the start of a comment line?

A. `//` B. `#` C. `/*`

**Correct Answer: B. `#`**. The hash symbol indicates that the rest of the line should be ignored by the shell, except when used in the shebang.

**End of Basic Syntax. Click "Next Level" to continue.**

Level 2: Control Flow and Loops

2.1 What is the correct way to start an `if` condition that checks if a variable `COUNT` is equal to 10 using the standard test command?

A. `if [ $COUNT == 10 ]` B. `if [ "$COUNT" -eq 10 ]` C. `if COUNT = 10`

**Correct Answer: B.** The **`-eq`** operator is used for **numeric equality** inside single square brackets (`[` or `test`). Spaces are mandatory.

2.2 Which operator is used for string equality within the `[[ ... ]]` (double bracket) conditional expression?

A. `-eq` B. `-st` C. `==`

**Correct Answer: C. `==`**. Inside `[[ ... ]]`, you use `==` for string comparison and the standard C-like operators (`-eq`, `-lt`, etc.) for numbers.

2.3 Which test operator checks if a file named `/tmp/data.log` exists and is a regular file?

A. `-d` B. `-f` C. `-e`

**Correct Answer: B. `-f`**. `-d` checks for a directory, and `-e` checks only for existence (file or directory).

2.4 What is the purpose of the `break` statement inside a `for` or `while` loop?

A. It skips the rest of the current iteration and continues with the next one. B. It immediately exits the entire loop. C. It pauses the script until the user presses a key.

**Correct Answer: B.** **`break`** terminates the loop entirely. **`continue`** is used to skip the current iteration.

2.5 Which of the following is the correct syntax for a simple `for` loop that iterates over a list of files?

A. `for file; do echo $file; done` B. `for file in files.txt; do echo $file; done` C. `for file in $(ls *.log); do echo "$file"; done`

**Correct Answer: C.** The structure is `for VAR in LIST; do ... done`. Command substitution `$(...)` provides the list of log files.

2.6 How do you perform basic arithmetic calculation (e.g., adding 5 to variable `X`) in Bash?

A. `X = $X + 5` B. `let X = $X + 5` C. `X=$((X + 5))`

**Correct Answer: C.** The **`$(( ))`** syntax is the standard, preferred way for evaluating arithmetic expressions and setting a variable. `let` is also valid but less common.

2.7 What is the purpose of the `case` statement structure in shell scripting?

A. To create an infinite loop. B. To define a block of code to be run later as a function. C. To select a block of code to execute based on matching a value against several patterns.

**Correct Answer: C.** `case` is typically used as an alternative to long, nested `if-elif-else` structures when checking a single value against multiple possibilities.

2.8 What is the file test operator that checks if a file is readable by the current user?

A. `-w` B. `-r` C. `-x`

**Correct Answer: B. `-r`**. `-w` checks for write access, and `-x` checks for execute access.

2.9 In a `while` loop, where does the conditional check occur?

A. At the end of the loop body. B. Before the loop body is executed. C. After every third iteration.

**Correct Answer: B.** A **`while`** loop checks the condition **before** each iteration, meaning the loop may never execute if the condition is initially false.

2.10 What is the Bash equivalent of a C-style `for (i=0; i<10; i++)` loop?

A. `for i in 1..10; do ... done` B. `while i < 10; do ... done` C. `for ((i=0; i<10; i++)); do ... done`

**Correct Answer: C.** The **`(( ))`** syntax allows for C-style arithmetic expressions and is ideal for numerical counting loops.

**End of Control Flow. Click "Next Level" to continue.**

Level 3: Functions and Advanced Concepts

3.1 What is the correct way to define a function named `cleanup` in Bash?

A. `function cleanup()` B. `def cleanup:` C. `cleanup () { ... }`

**Correct Answer: C. `cleanup () { ... }`**. This is the standard POSIX shell function definition format. `function cleanup { ... }` is also valid in Bash but less portable.

3.2 Inside a function, how do you access the first argument passed specifically to that function?

A. `$1` B. `$1` C. `$ARG1`

**Correct Answer: A. `$1`**. Positional parameters (`$1`, `$2`, etc.) are local to the function they are called in, just as they are in the main script body.

3.3 What command is used to send the output of a script to the file descriptor 1 (Standard Output)?

A. `read` B. `echo` or `printf` C. `cat`

**Correct Answer: B. `echo` or `printf`**. Both are fundamental commands for sending text output to **STDOUT (FD 1)**. `cat` reads from a file and sends its content to STDOUT.

3.4 What does the I/O redirection syntax `2> errors.txt` do?

A. Sends STDOUT (1) to `errors.txt`. B. Redirects STDERR (2) to the file `errors.txt`, overwriting the file. C. Appends both STDOUT and STDERR to `errors.txt`.

**Correct Answer: B.** `2` refers to **STDERR** (Standard Error). A single `>` means **overwrite**. Use `2>>` to append.

3.5 Which command can be used to process a text file line-by-line using a pattern matching language?

A. `tr` B. `cut` C. `awk`

**Correct Answer: C. `awk`**. `awk` is a powerful tool designed for **pattern scanning and processing** text files, often used for field-based manipulation.

3.6 What is the Bash syntax for creating a local variable named `temp_count` inside a function?

A. `global temp_count=0` B. `temp_count=0` (variables are local by default in functions) C. `local temp_count=0`

**Correct Answer: C. `local temp_count=0`**. Without the `local` keyword, the variable would be global, potentially overwriting a variable in the main script.

3.7 What is the purpose of the `trap` command in shell scripting?

A. To create a function that runs when the script starts. B. To specify a command to execute when the script receives a signal (e.g., EXIT, INT, TERM). C. To capture network packets for security analysis.

**Correct Answer: B.** `trap` is essential for creating robust scripts that can clean up temporary files (using `trap cleanup EXIT`) or handle user interruptions gracefully.

3.8 Which utility is best suited for quickly extracting the second comma-separated field (column) from each line of a file?

A. `grep -c` B. `cut -d, -f2` C. `tr -d,`

**Correct Answer: B. `cut -d, -f2`**. `cut` is the tool for field/column extraction. `-d` sets the delimiter (comma), and `-f2` selects the second field.

3.9 In the command `find . -name "*.tmp" | xargs rm`, what is the primary role of `xargs`?

A. To find files with the `.tmp` extension. B. To convert the output of `find` into arguments for the `rm` command. C. To count the number of files found by `find`.

**Correct Answer: B.** `xargs` takes standard input (the list of files from `find`) and builds and executes command lines (`rm`) using that input as arguments.

3.10 What is the purpose of the `set -e` command often placed near the start of robust shell scripts?

A. It displays every command before it's executed. C. It causes the script to exit immediately if any command returns a non-zero exit status. B. It ensures all variables are treated as local.

**Correct Answer: B.** `set -e` (errexit) is crucial for preventing a script from continuing to run if a necessary prerequisite command fails.

**Shell Scripting Mastered! Click "Finish Quiz" to see your final summary.**

Final Quiz Summary 📋

Related Topics & Tags

Linux Bash ShellScripting Automation Variables ControlFlow Loops Functions IO-Redirection `awk` `sed` SysAdmin DevOps

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