String length (${#var}) in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the length of the string stored in variable name.

Bash Scripting

echo [1]

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

A$name

B$#name

C${name#}

D${#name}

Attempts:

3 left

💡 Hint

Common Mistakes

Using just $name prints the string, not its length.

Using ${name#} is incorrect syntax for length.

Using $#name is invalid in this context.

In bash, ${#var} gives the length of the string stored in var. So ${#name} prints the length of name.

2fill in blank

medium

Complete the code to store the length of word into variable len.

Bash Scripting

len=[1]

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

A${word#}

B$word

C${#word}

D$#word

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning len=$word stores the string, not its length.

Using ${word#} is invalid for length.

Using $#word is incorrect syntax.

Assigning len=${#word} stores the length of word in len.

3fill in blank

hard

Fix the error in the code to correctly print the length of text.

Bash Scripting

echo [1]

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

A${#text}

B${text#}

C$#text

D${text}

Attempts:

3 left

💡 Hint

Common Mistakes

Using ${text} prints the string, not its length.

Using $#text is invalid syntax.

Using ${text#} is incorrect.

Only ${#text} correctly prints the length of the string stored in text.

4fill in blank

hard

Fill both blanks to create a loop that prints each word and its length from the list words.

Bash Scripting

for word in [1]; do
  echo "$word: $[2]"
done

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

A"${words[@]}"

B${#word}

C${word}

Dwords

Attempts:

3 left

💡 Hint

Common Mistakes

Using just words without quotes or array syntax causes errors.

Using ${word} instead of ${#word} prints the word, not its length.

The loop iterates over all elements in the array words using "${words[@]}". Inside the loop, ${#word} gives the length of the current word.

5fill in blank

hard

Fill all three blanks to create a dictionary-like output of words and their lengths from list.

Bash Scripting

declare -A lengths
for [1] in [2]; do
  lengths[[1]]=[3]
done
for key in "${!lengths[@]}"; do
  echo "$key: ${lengths[$key]}"
done

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

Aitem

B"${list[@]}"

C${#item}

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using list without quotes or array syntax causes errors.

Using ${item} instead of ${#item} stores the word, not its length.

Using inconsistent variable names inside the loop.

The loop uses item as the variable, iterates over all elements in list with "${list[@]}", and stores the length of each item with ${#item}.

Practice

1. What does the expression ${#var} do in a bash script?

easy

A. It converts the variable var to uppercase.

B. It returns the value of the variable var.

C. It counts the number of words in the variable var.

D. It returns the length of the string stored in the variable var.

Solution

1. Step 1: Understand the syntax ${#var}

   This syntax in bash returns the length of the string stored in the variable var.

2. Step 2: Differentiate from other operations

   It does not return the value itself, count words, or change case. It specifically counts characters.

3. Final Answer:

   It returns the length of the string stored in the variable var. -> Option D

4. Quick Check:

   Length of string = ${#var} [OK]

Hint: Remember: ${#var} counts characters in var [OK]

Common Mistakes:

• Confusing ${#var} with $var (value of variable)
• Thinking it counts words instead of characters
• Assuming it changes the string content

2. Which of the following is the correct way to get the length of a string variable name in bash?

easy

A. length=${name#}

B. length=$#name

C. length=${#name}

D. length=$name#

Solution

1. Step 1: Recall correct syntax for string length

   The correct syntax to get string length is ${#variable}, so for name it is ${#name}.

2. Step 2: Check each option

   length=${name#} uses wrong placement of #, length=$#name uses $ and # incorrectly, length=$name# appends # after variable incorrectly.

3. Final Answer:

   length=${#name} -> Option C

4. Quick Check:

   Use ${#var} to get length [OK]

Hint: Use ${#var} exactly to get string length [OK]

Common Mistakes:

• Placing # after variable name instead of before
• Using $# which counts positional parameters, not string length
• Confusing variable expansion syntax

3. What will be the output of the following bash script?

text="Hello World"
echo ${#text}

medium

A. 11

B. Error

C. 12

D. 10

Solution

1. Step 1: Count characters in the string "Hello World"

   The string has 11 characters: 5 letters in "Hello", 1 space, and 5 letters in "World".

2. Step 2: Understand ${#text} returns string length

   The command echo ${#text} prints the length, which is 11.

3. Final Answer:

   11 -> Option A

4. Quick Check:

   Length of "Hello World" = 11 [OK]

Hint: Count spaces too when using ${#var} [OK]

Common Mistakes:

• Ignoring spaces in length count
• Counting words instead of characters
• Expecting output to be string value instead of length

4. Consider this bash script snippet:

myvar=Hello
length=$#myvar
echo $length

What is the problem with this script?

medium

A. It will print the number of positional parameters, not string length.

B. It will print the length of the string correctly.

C. It will cause a syntax error due to wrong variable name.

D. It will print the string value instead of length.

Solution

1. Step 1: Understand what $# means in bash

   The symbol $# returns the number of positional parameters passed to the script, not the length of a string variable.

2. Step 2: Analyze the script behavior

   Assigning length=$#myvar tries to get positional parameters count, ignoring myvar. So it does not get string length.

3. Final Answer:

   It will print the number of positional parameters, not string length. -> Option A

4. Quick Check:

   $# counts parameters, not string length [OK]

Hint: Use ${#var} for length, not $# [OK]

Common Mistakes:

• Confusing $# (positional params) with ${#var} (string length)
• Expecting $# to work on variables
• Missing braces around variable name

5. You want to check if a user input stored in variable input is empty or not in a bash script. Which condition correctly uses string length to do this?

hard

A. if [ $#input -eq 0 ]; then echo "Empty input"; fi

B. if [ ${#input} -eq 0 ]; then echo "Empty input"; fi

C. if [ $input -eq 0 ]; then echo "Empty input"; fi

D. if [ ${input#} -eq 0 ]; then echo "Empty input"; fi

Solution

1. Step 1: Use ${#input} to get string length

   To check if input is empty, we check if its length is zero using ${#input}.

2. Step 2: Write correct if condition syntax

   The condition [ ${#input} -eq 0 ] correctly tests if the string length is zero.

3. Final Answer:

   if [ ${#input} -eq 0 ]; then echo "Empty input"; fi -> Option B

4. Quick Check:

   Check empty string with ${#var} == 0 [OK]

Hint: Test empty string with if [ ${#var} -eq 0 ] [OK]

Common Mistakes:

• Using $#input which is invalid
• Comparing string value directly to number
• Misplacing # symbol in variable expansion