tr (translate characters) in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to translate all lowercase letters to uppercase using tr.

Linux CLI

echo "hello world" | tr [1]

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

A'a-z' 'A-Z'

BA-Z a-z

C0-9 a-z

Da-z 0-9

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of character sets.

Using numbers instead of letters.

Forgetting to quote the character sets.

The tr command translates characters from the first set to the second set. To convert lowercase to uppercase, use tr 'a-z' 'A-Z'.

2fill in blank

medium

Complete the code to delete all digits from the input using tr.

Linux CLI

echo "abc123def456" | tr -d [1]

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

Aa-z

B0-9

CA-Z

D[:alpha:]

Attempts:

3 left

💡 Hint

Common Mistakes

Deleting letters instead of digits.

Using uppercase letters as the set.

Not using the -d option.

The -d option deletes characters. To delete digits, use 0-9.

3fill in blank

hard

Fix the error in the code to replace all spaces with underscores using tr.

Linux CLI

echo "hello world" | tr [1]

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

A" _"

B"_ "

C" " "_"

D"_" " "

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of characters.

Missing quotes around characters.

Using the wrong characters inside quotes.

The correct syntax is tr ' ' '_' to replace spaces with underscores. Quotes are needed around each character set.

4fill in blank

hard

Fill both blanks to create a command that squeezes multiple spaces into one space and then deletes all digits.

Linux CLI

echo "a  b   c123" | tr [1] | tr -d [2]

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

A-s ' '

B0-9

Ca-z

D-d ' '

Attempts:

3 left

💡 Hint

Common Mistakes

Using -d instead of -s for squeezing.

Deleting letters instead of digits.

Incorrect order of commands.

Use tr -s ' ' to squeeze spaces and tr -d 0-9 to delete digits.

5fill in blank

hard

Fill all three blanks to create a command that converts lowercase to uppercase, deletes digits, and replaces spaces with underscores.

Linux CLI

echo "hello 123 world" | tr [1] | tr -d [2] | tr [3]

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

A"a-z" "A-Z"

B0-9

C" " "_"

D"A-Z" "a-z"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping uppercase and lowercase sets.

Forgetting to delete digits.

Incorrect quoting of characters.

First, convert lowercase to uppercase with tr 'a-z' 'A-Z'. Then delete digits with tr -d 0-9. Finally, replace spaces with underscores using tr ' ' '_'.

Practice

1. What does the tr command do in Linux?

easy

A. It translates or deletes characters from input text.

B. It lists files in a directory.

C. It compiles source code.

D. It displays the current directory path.

Solution

1. Step 1: Understand the purpose of tr

   The tr command is used to translate or delete characters from input text streams.

2. Step 2: Compare with other options

   Options A, C, and D describe other commands like ls, compilers, and pwd, which are unrelated to tr.

3. Final Answer:

   It translates or deletes characters from input text. -> Option A

4. Quick Check:

   tr = translate/delete chars [OK]

Hint: Remember: tr = translate characters [OK]

Common Mistakes:

• Confusing tr with ls or pwd commands
• Thinking tr compiles code
• Assuming tr lists files

2. Which of the following is the correct syntax to replace all lowercase 'a' characters with 'b' using tr?

easy

A. tr -replace a b

B. tr a-z b

C. tr 'a' 'b'

D. tr 'a' to 'b'

Solution

1. Step 1: Recall tr syntax

   The correct syntax uses single quotes around the sets of characters: tr 'a' 'b'.

2. Step 2: Evaluate options

   tr a-z b uses a range which translates all lowercase letters to 'b' (padded), incorrect for only 'a'. Options A and C use invalid syntax for tr.

3. Final Answer:

   tr 'a' 'b' -> Option C

4. Quick Check:

   Use quotes around sets in tr [OK]

Hint: Use quotes around characters in tr command [OK]

Common Mistakes:

• Using range 'a-z' for single character
• Using invalid options like -replace
• Adding extra words like 'to'

3. What is the output of the command:
echo "hello world" | tr 'a-z' 'A-Z'?

medium

A. HELLO WORLD

B. hello world

C. HELLO world

D. Error: invalid range

Solution

1. Step 1: Understand the command

   The command converts all lowercase letters (a-z) to uppercase (A-Z) in the input text "hello world".

2. Step 2: Apply translation

   All letters become uppercase, so "hello world" becomes "HELLO WORLD".

3. Final Answer:

   HELLO WORLD -> Option A

4. Quick Check:

   Lowercase to uppercase translation = HELLO WORLD [OK]

Hint: tr 'a-z' 'A-Z' converts lowercase to uppercase [OK]

Common Mistakes:

• Expecting partial uppercase
• Confusing input and output
• Thinking it causes an error

4. Identify the error in this command:
echo "123abc" | tr '0-9' 'a-j'

medium

A. Ranges in sets are mismatched length causing error

B. No error, command works correctly

C. Output will be empty

D. Quotes are missing around sets

Solution

1. Step 1: Analyze the command

   The command replaces digits 0-9 with letters a-j. Both sets have equal length (10 characters).

2. Step 2: Check for syntax or runtime errors

   Quotes are present, ranges are valid and equal length, so no error occurs.

3. Final Answer:

   No error, command works correctly -> Option B

4. Quick Check:

   Equal length ranges with quotes = valid command [OK]

Hint: Ensure equal length sets in tr to avoid errors [OK]

Common Mistakes:

• Assuming mismatched lengths cause errors here
• Missing quotes around sets
• Expecting output to be empty

5. You want to remove all vowels (a, e, i, o, u) from a text file named input.txt. Which command correctly does this using tr?

hard

A. tr -remove 'aeiou' < input.txt

B. tr 'aeiou' < input.txt

C. tr -r 'aeiou' < input.txt

D. tr -d 'aeiou' < input.txt

Solution

1. Step 1: Understand the goal

   The goal is to delete vowels from the input text file.

2. Step 2: Identify correct tr option

   The -d option deletes specified characters. So tr -d 'aeiou' removes vowels.

3. Step 3: Check other options

   tr 'aeiou' < input.txt lacks the second character set, causing an error. Options C and D use invalid options.

4. Final Answer:

   tr -d 'aeiou' < input.txt -> Option D

5. Quick Check:

   Use -d to delete chars in tr [OK]

Hint: Use tr -d to delete characters from input [OK]

Common Mistakes:

• Missing second character set operand
• Using invalid options like -r or -remove
• Forgetting to redirect input