Which sequence sends only standard error to a file while leaving standard output untouched?

• A. 2> file.txt
• B. > file.txt
• C. &> file.txt
• D. 1> file.txt

Answer: (A)

In Unix-like shells, standard output is file descriptor 1 and standard error is file descriptor 2. To send only the error messages to a file while keeping normal output on the screen, you redirect the second descriptor. The syntax 2> file.txt does exactly that: it sends only stderr to file.txt, leaving stdout untouched. The other options redirect stdout ( > file.txt or 1> file.txt ) or redirect both streams ( &> file.txt ), which isn’t what the question asks.