Interview Q&A / Linux & Shell

1. How do Ctrl+Z, bg, fg and jobs work in a shell?

   Ctrl+Z suspends the foreground job, bg resumes it in the background, fg brings it back to the foreground and jobs lists the shell's jobs with numbers. Appending & to a command starts it in the background directly.

   BeginnerQuick answer1 min read
2. How do you find or stop processes by name using pgrep and pkill?

   pgrep prints the PIDs of processes whose names match a pattern, and pkill sends them a signal (SIGTERM by default). Use -f to match the full command line and -u to limit to a user. Always run pgrep first to see what would be hit.

   BeginnerQuick answer1 min read
3. What is the difference between ps aux and ps -ef?

   Both list every process on the system. ps aux uses BSD-style options and shows %CPU, %MEM and memory sizes; ps -ef uses the POSIX style and shows the parent PID (PPID) and full start time. Choose aux for resource use and -ef for process relationships.

   BeginnerQuick answer1 min read
4. What is the difference between running a command with & and with nohup?

   & only puts the command in the background of the current shell; it can still die when the terminal closes. nohup makes the command ignore the hangup signal, so it keeps running after logout, and sends its output to nohup.out unless redirected.

   BeginnerQuick answer1 min read