As the root user, which command lists all processes running as root and displays their names?

• A. ps -ef | grep root
• B. pgrep -u root -l
• C. ps -U root -o pid,comm
• D. top -u root

Answer: (B)

The key is filtering processes by the user identity that determines who is currently running each process. Using pgrep with the effective-user filter and asking for the names gives a clean, precise list of what root is actually running right now.

pgrep -u root -l searches for processes owned by the effective user root (user id 0) and prints the names of those processes. The -u root part targets processes running as root now, and -l makes the command print the process names, yielding a straightforward list of root-owned process names.

Other options aren’t as precise or convenient. Using ps -ef | grep root can catch any process whose command line contains the string root, not necessarily processes owned by root, and you’d have to weed out the grep process itself. ps -U root -o pid,comm filters by the real user ID, which isn’t the same as the effective user ID that determines who is “running as” root in typical use. top -u root is interactive and shows dynamic usage statistics rather than a simple, static list of names.

So the best choice is the one that directly filters by the effective root user and lists the process names in a concise, non-interactive format.