Uppercase and lowercase conversion in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this Bash command?

Consider the following command that converts a string to uppercase. What will it output?

Bash Scripting

echo "hello World" | tr '[:lower:]' '[:upper:]'

A hello World

B HELLO WORLD

C Hello World

D HELLO world

💡 Hint

The tr command replaces characters from one set to another.

The tr command with '[:lower:]' and '[:upper:]' converts all lowercase letters to uppercase. So 'hello World' becomes 'HELLO WORLD'.

💻 Command Output

intermediate

What is the output of this Bash command?

What will this command output when converting a string to lowercase?

Bash Scripting

echo "BASH SCRIPTING" | tr '[:upper:]' '[:lower:]'

A bash scripting

B BASH SCRIPTING

C Bash Scripting

D bash SCRIPTING

💡 Hint

The tr command changes uppercase letters to lowercase letters.

The tr command replaces all uppercase letters with lowercase letters, so 'BASH SCRIPTING' becomes 'bash scripting'.

📝 Syntax

advanced

Which option correctly converts a variable to uppercase in Bash?

Given a variable name VAR="hello", which command correctly converts its value to uppercase?

Bash Scripting

VAR="hello"

A echo ${VAR^^:}

B echo ${VAR^^^}

C echo ${VAR^^?}

D echo ${VAR^^}

💡 Hint

Use Bash parameter expansion for case conversion.

In Bash 4+, ${VAR^^} converts all characters in VAR to uppercase. Other options are invalid syntax.

💻 Command Output

advanced

What is the output of this Bash script snippet?

What will this script output?

Bash Scripting

input="HeLLo WoRLd"
echo "$input" | awk '{print tolower($0)}'

A hello world

B HeLLo WoRLd (unchanged)

C HELLO WORLD

D HeLLo WoRLd

💡 Hint

awk's tolower function converts text to lowercase.

The awk command with tolower converts the entire input string to lowercase, so output is 'hello world'.

🚀 Application

expert

How many lines will be printed by this script?

This script reads lines from a file and prints only those lines that are uppercase. How many lines will it print?

Bash Scripting

while IFS= read -r line; do
  if [[ "$line" == "${line^^}" ]]; then
    echo "$line"
  fi
done < input.txt

A No lines will be printed

B All lines regardless of case

C Only lines that are fully uppercase

D Only lines that are fully lowercase

💡 Hint

The condition compares the line to its uppercase version.

The script prints lines where the original line equals its uppercase version, meaning the line is fully uppercase.

Practice

1. In bash scripting, which syntax converts the value of a variable name to all uppercase letters?

easy

A. Using uppercase(name)

B. Using ${name,,}

C. Using ${name^^}

D. Using toUpperCase(name)

Solution

1. Step 1: Understand bash variable expansion for case conversion

   Bash supports ${variable^^} to convert all letters in variable to uppercase.

2. Step 2: Compare options with bash syntax

   Using ${name^^} uses ${name^^}, which is the correct bash syntax. Using ${name,,} converts to lowercase, and options C and D are not valid bash syntax.

3. Final Answer:

   Using ${name^^} -> Option C

4. Quick Check:

   Uppercase conversion = ${variable^^} [OK]

Hint: Use ${variable^^} to uppercase text in bash [OK]

Common Mistakes:

• Confusing uppercase and lowercase syntax
• Using non-bash functions like toUpperCase()
• Forgetting the double caret ^^

2. Which of the following is the correct syntax to convert the variable text to lowercase in bash?

easy

A. echo ${text,,}

B. echo ${text^^}

C. echo ${text^}

D. echo ${text,}

Solution

1. Step 1: Recall lowercase conversion syntax in bash

   To convert all letters to lowercase, bash uses ${variable,,}.

2. Step 2: Analyze each option

   echo ${text,,} uses ${text,,} which converts all letters to lowercase. echo ${text^^} converts to uppercase, C and D convert only the first letter.

3. Final Answer:

   echo ${text,,} -> Option A

4. Quick Check:

   Lowercase conversion = ${variable,,} [OK]

Hint: Use ${variable,,} to lowercase all letters in bash [OK]

Common Mistakes:

• Using single comma instead of double for all letters
• Mixing uppercase and lowercase syntax
• Confusing ^ and , operators

3. What is the output of the following bash script?

word="HelloWorld"
echo ${word,,}

medium

A. helloworld

B. helloWorld

C. HelloWorld

D. HELLOWORLD

Solution

1. Step 1: Understand the variable and conversion

   The variable word contains "HelloWorld". The expression ${word,,} converts all letters to lowercase.

2. Step 2: Apply lowercase conversion

   Converting "HelloWorld" to lowercase results in "helloworld".

3. Final Answer:

   helloworld -> Option A

4. Quick Check:

   Lowercase conversion of HelloWorld = helloworld [OK]

Hint: Lowercase all letters with ${variable,,} [OK]

Common Mistakes:

• Expecting only first letter to change
• Confusing uppercase and lowercase syntax
• Ignoring case conversion operator

4. The following bash script is intended to convert input to uppercase, but it does not work as expected:

input="bashScript"
echo $input^^

What is the error?

medium

A. Variable name is incorrect

B. Missing braces around the variable for case conversion

C. Using single caret instead of double caret

D. Uppercase conversion is not supported in bash

Solution

1. Step 1: Identify correct syntax for uppercase conversion

   Bash requires braces around the variable when using case conversion, like ${input^^}.

2. Step 2: Analyze the script

   The script uses $input^^ without braces, which is invalid syntax and will not convert case.

3. Final Answer:

   Missing braces around the variable for case conversion -> Option B

4. Quick Check:

   Use ${variable^^} with braces for uppercase [OK]

Hint: Always use braces ${} for case conversion in bash [OK]

Common Mistakes:

• Omitting braces around variable
• Using single caret ^ for all letters
• Assuming bash lacks uppercase conversion

5. You have a list of filenames stored in a bash array: files=("Report1.txt" "summary2.TXT" "DATA3.Txt"). You want to convert all filenames to lowercase and print them line by line. Which script correctly does this?

hard

A. for f in "${files[@]}"; do echo tolower($f); done

B. for f in "${files[@]}"; do echo ${f^^}; done

C. for f in files; do echo ${f,,}; done

D. for f in "${files[@]}"; do echo ${f,,}; done

Solution

1. Step 1: Understand the goal and array iteration

   The goal is to convert each filename to lowercase and print it. Iterating over "${files[@]}" correctly accesses each element.

2. Step 2: Check each option's correctness

   for f in "${files[@]}"; do echo ${f,,}; done uses ${f,,} to convert to lowercase and iterates correctly. for f in "${files[@]}"; do echo ${f^^}; done converts to uppercase, C iterates incorrectly (missing quotes and array expansion), D uses a non-bash function tolower().

3. Final Answer:

   for f in "${files[@]}"; do echo ${f,,}; done -> Option D

4. Quick Check:

   Lowercase array elements with ${var,,} in loop [OK]

Hint: Use for loop with ${var,,} to lowercase array items [OK]

Common Mistakes:

• Using uppercase conversion instead of lowercase
• Incorrect array iteration syntax
• Using non-existent bash functions