What is the effect of echo test > file.txt 2>&1?

• A. Redirects stdout to file.txt; stderr to screen
• B. Redirects both stdout and stderr to file.txt
• C. Redirects stdout to file and leaves stderr unchanged
• D. Redirects input from file.txt

Answer: (B)

This is about how shell I/O redirection works. The command first sends stdout to file.txt with > file.txt. Then 2>&1 redirects stderr to wherever stdout is currently going. Since stdout is already going to file.txt, stderr is redirected there as well. So both stdout and stderr end up in file.txt. If the order were reversed, the result could be different, but with this left-to-right processing, both streams go to the file.