kill and signal types in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of sending SIGTERM to a process?

You run the command kill -15 1234 to send a SIGTERM signal to process 1234. What is the expected behavior if the process handles SIGTERM properly?

A The process terminates gracefully, cleaning up resources before exiting.

B The process immediately stops without cleanup.

C The process ignores the signal and continues running.

D The system restarts the process automatically.

💡 Hint

SIGTERM is a polite request to terminate a process.

SIGTERM (signal 15) asks a process to terminate gracefully. If the process handles it, it can clean up before exiting.

💻 Command Output

intermediate

What happens when you send SIGKILL to a process?

You execute kill -9 5678 to send SIGKILL to process 5678. What is the immediate effect?

A The process ignores the signal and continues running.

B The process is immediately terminated by the kernel without cleanup.

C The process receives a chance to save data before exiting.

D The process restarts automatically after termination.

💡 Hint

SIGKILL cannot be caught or ignored.

SIGKILL (signal 9) forces the kernel to stop the process immediately without giving it a chance to clean up.

📝 Syntax

advanced

Which kill command syntax sends SIGUSR1 to process 4321?

Choose the correct command to send the SIGUSR1 signal to process ID 4321.

A kill -usr1 4321

B kill -SIGUSR1 4321

C kill -signal SIGUSR1 4321

D kill -s SIGUSR1 4321

💡 Hint

Use the -s option to specify signal by name.

The correct syntax to send a named signal is 'kill -s SIGNAL PID'. Other forms are invalid or unsupported.

🔧 Debug

advanced

Why does kill -15 without a PID fail?

You run kill -15 without specifying a process ID. What error or behavior occurs?

A kill reports 'usage error' because PID is missing.

B kill sends SIGTERM to all processes owned by the user.

C kill sends SIGTERM to the shell itself.

D kill silently does nothing and exits with success.

💡 Hint

kill requires a PID argument to know which process to signal.

Without a PID, kill cannot send a signal and shows a usage error message.

🧠 Conceptual

expert

What signal number corresponds to SIGSTOP and what is its effect?

Identify the signal number for SIGSTOP and explain what happens to a process when it receives this signal.

A Signal 15; the process terminates gracefully.

B Signal 9; the process is terminated immediately.

C Signal 19; the process is paused and can be resumed later.

D Signal 1; the process ignores the signal.

💡 Hint

SIGSTOP pauses a process without terminating it.

SIGSTOP (usually signal 19) stops a process execution until it is resumed with SIGCONT.