Which command reads standard input and writes it out with every lowercase letter converted to uppercase?
LPIC-1 Exam 101-500, objective 103. GNU and Unix commands medium
Machine-checked — no person has signed for it. This question was read against the source cited below by an automated pass, which found no contradiction. That is a weaker claim than it sounds: the same kind of process wrote the question, so it can confirm its own mistake.
Treat it as a good draft rather than as settled fact, and read the source below before you rely on it. It is not used in mock exams here — only questions a person has signed for are.
How these questions are written — where each question comes from, what the verification ledger records, and what happens when one is found wrong.
The options
Not correct tr -s 'a-z'
Wrong. -s squeezes repeats: a run of the same character from the set is collapsed into one. It changes nothing about case.
Not correct tr -d 'a-z'
Wrong. -d DELETES every character in the set, so all lowercase letters disappear from the output.
Correct tr 'a-z' 'A-Z'
Correct. tr maps each character of the first set to the character at the same position in the second set, so a becomes A, b becomes B, and so on.
Not correct sed 's/a-z/A-Z/'
Wrong. Without a character class this substitutes the literal text "a-z" with "A-Z" once per line. A working sed version would be sed 's/[a-z]/\U&/g' with GNU sed.
Why
tr translates or deletes characters read from standard input; it takes no file arguments, so you always feed it through a pipe or a redirect. The common forms are `tr 'a-z' 'A-Z'` (or the portable `tr '[:lower:]' '[:upper:]'`), `tr -d` to delete a set, and `tr -s` to squeeze repeated characters.
Where this comes from
- Cited
- LPI exam objective 103.2
- What it says
- Use tr to translate, delete and squeeze characters in a text stream.
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 103 and space the ones you get wrong.
More questions on this objective
- A user starts a new terminal window in a running graphical desktop session, which launches bash as an interactive shell that is NOT a login shell. Which file in the user's home directory does bash read in that case? machine-checked
- In bash, which history expansion re-runs the entire previous command line? machine-checked
- Which bash command prints the literal five characters $USER instead of the current user name? machine-checked
- You want /opt/bin searched for executables, after all the directories already in PATH, in the current bash session and in every command started from it. Which command does that? machine-checked
- There is a passwd manual page in section 1 (the command) and another in section 5 (the /etc/passwd file format). Which command opens the section 5 page? machine-checked
- Select the TWO true statements about shell variables and the environment in bash. machine-checked