Configuration file reading in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read a configuration file line by line.

Bash Scripting

while IFS= read -r [1]; do
  echo "$line"
done < config.txt

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

Afile

Bconfig

Cline

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not used later in the loop.

Forgetting to use 'read -r' to prevent backslash escapes.

The variable 'line' is commonly used to store each line read from the file.

2fill in blank

medium

Complete the code to extract the value of 'username' from the config file.

Bash Scripting

username=$(grep '^username=' config.txt | cut -d'=' -f[1])

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

A2

B0

C3

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using field 1 which returns the key, not the value.

Using field 0 which is invalid.

The value is after the '=' sign, which is the second field when splitting by '='.

3fill in blank

hard

Fix the error in the code to ignore empty lines and comments starting with '#'.

Bash Scripting

while IFS= read -r line; do
  if [[ ! $line =~ ^# ]] && [[ -n $[1] ]]; then
    echo "$line"
  fi
done < config.txt

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

Afile

Bline

Cconfig

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that was not defined.

Not checking for empty lines properly.

The condition checks if the variable 'line' is not empty and does not start with '#'.

4fill in blank

hard

Fill both blanks to create a dictionary (associative array) from config file lines with key=value format.

Bash Scripting

declare -A config
while IFS='=' read -r [1] [2]; do
  config[$key]=$value
done < config.txt

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

Akey

Bval

Cvalue

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names that don't match the assignment.

Using the same variable name for both key and value.

The first blank is the key variable, the second blank is the value variable.

5fill in blank

hard

Fill all three blanks to print all keys and values from the associative array.

Bash Scripting

for [1] in "${!config[@]}"; do
  echo "[2] = ${config[[3]]}"
done

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

Akey

Bconfig

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in the loop and inside the echo statement.

Using the array name instead of the key variable.

The loop variable is 'key', used to access keys and values in the array.

Practice

1. What is the main purpose of reading a configuration file in a bash script?

easy

A. To load variable values that the script can use

B. To execute commands from the internet

C. To delete files automatically

D. To compile the script into a binary

Solution

1. Step 1: Understand configuration files

   Configuration files usually contain variable assignments that scripts read to get settings.

2. Step 2: Purpose of reading config files

   Reading these files allows scripts to use flexible values without hardcoding them.

3. Final Answer:

   To load variable values that the script can use -> Option A

4. Quick Check:

   Config files provide variables = B [OK]

Hint: Config files store variables for scripts to use [OK]

Common Mistakes:

• Thinking config files run commands directly
• Confusing config files with executable scripts
• Assuming config files delete or compile code

2. Which of the following is the correct syntax to read a config file named settings.conf in a bash script?

easy

A. source settings.conf

B. read settings.conf

C. import settings.conf

D. execute settings.conf

Solution

1. Step 1: Identify the command to read config files

   In bash, source or . is used to read and execute commands from a file in the current shell.

2. Step 2: Check options

   read reads input, import is not a bash command, and execute is invalid.

3. Final Answer:

   source settings.conf -> Option A

4. Quick Check:

   Use source or . to read config [OK]

Hint: Use 'source' or '.' to load config files [OK]

Common Mistakes:

• Using 'read' command instead of 'source'
• Trying to 'import' like in other languages
• Assuming 'execute' runs the config file

3. Given the config file app.conf with content:

USERNAME=guest
PORT=8080

What will the output of this script be?

source app.conf
echo "User: $USERNAME, Port: $PORT"

medium

A. User: $USERNAME, Port: $PORT

B. User: , Port:

C. Syntax error

D. User: guest, Port: 8080

Solution

1. Step 1: Source the config file

   The source app.conf command loads variables USERNAME and PORT into the script.

2. Step 2: Print the variables

   The echo command prints the values of USERNAME and PORT, which are 'guest' and '8080'.

3. Final Answer:

   User: guest, Port: 8080 -> Option D

4. Quick Check:

   Variables loaded and printed = C [OK]

Hint: Sourcing sets variables, echo prints their values [OK]

Common Mistakes:

• Not sourcing the file before using variables
• Expecting variable names printed literally
• Confusing syntax causing errors

4. What is wrong with this script snippet that tries to read config.cfg and print a variable?

source config.cfg
echo "Value: $VALUE"

Assuming config.cfg contains VALUE=42, but the output is empty.

medium

A. The script forgot to use 'export' before sourcing

B. The config file has spaces around '=' causing no assignment

C. The variable name is case-sensitive and mismatched

D. The source command is misspelled

Solution

1. Step 1: Check config file syntax

   If the config file has spaces like VALUE = 42, bash treats it as a command, not assignment.

2. Step 2: Effect on sourcing

   Because of wrong syntax, VALUE is not set, so echo prints empty.

3. Final Answer:

   The config file has spaces around '=' causing no assignment -> Option B

4. Quick Check:

   No spaces in var assignment = A [OK]

Hint: No spaces around '=' in config files [OK]

Common Mistakes:

• Adding spaces around '=' in variable assignments
• Thinking 'export' is needed before sourcing
• Ignoring case sensitivity of variable names

5. You want to safely read a config file settings.conf that might contain unsafe commands. Which approach is best to avoid running unwanted code while still getting variable values?

hard

A. Run the config file as a separate script

B. Use source settings.conf directly without checks

C. Manually parse the file line-by-line to extract variable assignments

D. Delete the config file before sourcing

Solution

1. Step 1: Understand risks of sourcing

   Using source runs all commands in the file, which can be unsafe if file is untrusted.

2. Step 2: Safe alternative

   Manually reading lines and extracting only variable assignments avoids executing harmful commands.

3. Final Answer:

   Manually parse the file line-by-line to extract variable assignments -> Option C

4. Quick Check:

   Parse manually to avoid unsafe code = A [OK]

Hint: Parse config lines manually to avoid running code [OK]

Common Mistakes:

• Sourcing untrusted config files directly
• Running config as a script without validation
• Deleting config file instead of securing it