Script testing strategies in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run a script and check its exit status.

Bash Scripting

bash [1]; echo $?  # Prints the exit status of the script

Drag options to blanks, or click blank then click option'

Amyscript.sh

Brun.sh

Cscript.py

Dtest.sh

Attempts:

3 left

💡 Hint

Common Mistakes

Using a Python script name instead of a bash script.

Forgetting to specify the script file name.

The command 'bash myscript.sh' runs the script named 'myscript.sh'.

2fill in blank

medium

Complete the code to test if a variable is empty in a bash script.

Bash Scripting

if [ -z [1] ]; then echo "Empty"; fi

Drag options to blanks, or click blank then click option'

A$var

Bvar

C"var"

D$var.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Not using the $ sign before the variable name.

Using quotes incorrectly around the variable.

The syntax '-z $var' checks if the variable 'var' is empty.

3fill in blank

hard

Fix the error in the code to correctly test if a file exists.

Bash Scripting

if [[ -f [1] ]]; then echo "File exists"; fi

Drag options to blanks, or click blank then click option'

Afilename.txt

Bfilename

C"filename"

D$filename

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the $ sign before the variable.

Using single brackets [ ] with variable without quotes.

Use '$filename' to reference the variable holding the file name.

4fill in blank

hard

Fill both blanks to create a loop that tests each file in a directory.

Bash Scripting

for file in [1]; do if [[ -f [2] ]]; then echo "$file exists"; fi; done

Drag options to blanks, or click blank then click option'

A"*"

B$file

Cfile

D"file"

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the '*' wildcard.

Using 'file' without $ to reference the variable.

The loop iterates over all files with '*', and tests each with '$file'.

5fill in blank

hard

Fill all three blanks to create a function that tests if input is a directory and prints a message.

Bash Scripting

check_dir() {
  if [[ -d [1] ]]; then
    echo "[2] is a directory"
  else
    echo "Not a directory"
  fi
}

Drag options to blanks, or click blank then click option'

A$1

B"$1"

Dinput

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the variable, causing errors with spaces.

Using variable names instead of positional parameters.

Use "$1" to safely reference the first argument as a directory path and print it.

Practice

1. Why is it important to test a bash script before using it in real tasks?

easy

A. To reduce the script's file size

B. To make the script run faster automatically

C. To change the script's language to another programming language

D. To find and fix errors early, avoiding bigger problems later

Solution

1. Step 1: Understand the purpose of testing scripts

   Testing helps catch mistakes before the script runs on important data or systems.

2. Step 2: Identify the benefit of early error detection

   Finding errors early prevents failures and saves time and effort in fixing issues later.

3. Final Answer:

   To find and fix errors early, avoiding bigger problems later -> Option D

4. Quick Check:

   Testing = Catch errors early [OK]

Hint: Testing finds errors before damage happens [OK]

Common Mistakes:

• Thinking testing makes scripts faster automatically
• Confusing testing with rewriting code
• Believing testing reduces file size

2. Which command is used to run a bash script with debugging output showing each command executed?

easy

A. bash -e script.sh

B. bash -v script.sh

C. bash -x script.sh

D. bash -c script.sh

Solution

1. Step 1: Recall bash debugging options

   The -x option runs the script showing each command before execution.

2. Step 2: Differentiate from other options

   -v prints shell input lines, -e exits on error, -c runs commands from string.

3. Final Answer:

   bash -x script.sh -> Option C

4. Quick Check:

   Debug with -x = bash -x [OK]

Hint: Use bash -x to see commands run step-by-step [OK]

Common Mistakes:

• Confusing -v with -x for debugging
• Using -e expecting debug output
• Trying -c without command string

3. What will be the output of this script when run with bash -x test.sh?

#!/bin/bash
x=5
if [ $x -gt 3 ]; then
  echo "Greater"
else
  echo "Smaller"
fi

medium

A. + x=5
+ '[' 5 -gt 3 ']'
+ echo 'Greater'
Greater

B. Greater

C. + x=5
+ echo 'Greater'
Greater

D. Smaller

Solution

1. Step 1: Understand bash -x output

   Running with -x prints each command with a plus sign before executing it.

2. Step 2: Trace the script commands

   Commands x=5, the test [ $x -gt 3 ], and echo "Greater" are printed before output.

3. Final Answer:

   + x=5 + '[' 5 -gt 3 ']' + echo 'Greater' Greater -> Option A

4. Quick Check:

   bash -x shows commands with + [OK]

Hint: bash -x shows commands with + before output [OK]

Common Mistakes:

• Ignoring the debug lines starting with +
• Choosing output without debug info
• Confusing else branch output

4. This script is intended to check if a file exists and print a message, but it fails. What is the error?

#!/bin/bash
filename="myfile.txt"
if [ -f $filename ]
then
  echo "File exists"
else
  echo "File missing"
fi

medium

A. The if statement syntax is incorrect; should use double brackets [[ ]]

B. Missing quotes around $filename can cause errors if filename has spaces

C. The script needs to use -e instead of -f to check file existence

D. The echo commands must be inside curly braces { }

Solution

1. Step 1: Identify variable usage in test condition

   The variable $filename is unquoted, which can cause errors if it contains spaces.

2. Step 2: Understand quoting importance in bash tests

   Quoting variables prevents word splitting and errors in test expressions.

3. Final Answer:

   Missing quotes around $filename can cause errors if filename has spaces -> Option B

4. Quick Check:

   Quote variables in tests = Missing quotes around $filename can cause errors if filename has spaces [OK]

Hint: Always quote variables in test conditions [OK]

Common Mistakes:

• Thinking [[ ]] is required instead of [ ]
• Confusing -f and -e options
• Believing echo needs braces

5. You want to test a script that processes user input and exits with code 0 on success or 1 on failure. Which strategy best helps automate testing this behavior?

hard

A. Write test cases that run the script with different inputs and check the exit code using $?

B. Only run the script manually and watch the output on screen

C. Use echo statements inside the script without checking exit codes

D. Rename the script file to .test and run it without arguments

Solution

1. Step 1: Understand exit codes in bash scripts

   Scripts use exit codes to signal success (0) or failure (non-zero).

2. Step 2: Automate testing by running script with inputs and checking $?

   Running script with inputs and verifying $? confirms correct behavior automatically.

3. Final Answer:

   Write test cases that run the script with different inputs and check the exit code using $? -> Option A

4. Quick Check:

   Test exit codes with $? = Write test cases that run the script with different inputs and check the exit code using $? [OK]

Hint: Check $? after running script to verify success/failure [OK]

Common Mistakes:

• Relying only on manual output checks
• Ignoring exit codes in tests
• Assuming renaming files triggers tests