tr for character transformation in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the tr command do in bash scripting?

The tr command translates or deletes characters from input. It is used to transform characters, like changing lowercase letters to uppercase.

beginner

How do you use tr to convert all lowercase letters to uppercase?

Use tr 'a-z' 'A-Z'. It replaces every lowercase letter with its uppercase equivalent.

intermediate

What happens if the input contains characters not in the first set of tr?

Characters not in the first set are passed through unchanged. tr only transforms characters it matches in the first set.

intermediate

How can you delete characters using tr?

Use the -d option with the characters to delete. For example, tr -d 'aeiou' deletes all vowels from the input.

beginner

Explain the difference between tr 'a-z' 'A-Z' and tr 'A-Z' 'a-z'.

tr 'a-z' 'A-Z' converts lowercase letters to uppercase. tr 'A-Z' 'a-z' converts uppercase letters to lowercase.

Which tr command converts all lowercase letters to uppercase?

A tr 'a-z' 'A-Z'

B tr 'A-Z' 'a-z'

C tr -d 'a-z'

D tr '0-9' 'a-z'

The command tr 'a-z' 'A-Z' replaces lowercase letters with uppercase letters.

What does tr -d 'aeiou' do?

A Converts vowels to uppercase

B Replaces vowels with numbers

C Deletes all vowels from input

D Duplicates vowels in input

The -d option deletes specified characters, so vowels are removed.

If input contains digits and you run tr 'a-z' 'A-Z', what happens to digits?

A Digits remain unchanged

B Digits are deleted

C Digits are converted to uppercase letters

D Digits are replaced with spaces

Characters not in the first set are passed through unchanged.

Which command deletes all spaces from input?

A tr -s ' '

B tr ' ' '-'

C tr 'a-z' 'A-Z'

D tr -d ' '

tr -d ' ' deletes all space characters.

What is the output of echo 'Hello123' | tr 'A-Z' 'a-z'?

A HELLO123

B hello123

C Hello123

D hELLO123

This converts uppercase letters to lowercase, digits remain unchanged.

Describe how to use tr to change all lowercase letters in a text to uppercase.

Think about replacing one set of characters with another.

Explain how to remove specific characters from input using tr.

Deleting means removing characters completely.