How to use the command 'killall' (with examples)

The ‘killall’ command is used to send a kill signal to all instances of a process by name. It is important to note that the process name must be an exact match. By default, ‘killall’ sends the SIGTERM (terminate) signal to terminate the process. However, other signals can be used to control the termination process. This command provides a simple way to terminate multiple instances of a process at once.

Use case 1: Terminate a process using the default SIGTERM signal

Code:

killall process_name

Motivation: This use case is used to terminate a process using the default signal. It is particularly useful when you want to stop a process gracefully without killing it abruptly. Terminating a process with SIGTERM allows the process to perform necessary cleanup tasks before exiting.

Explanation: In this use case, the ‘killall’ command is used to terminate a process named ‘process_name’. The command will send the SIGTERM signal to all instances of the process with the matching name.

Example output: The process named ‘process_name’ will receive the SIGTERM signal and execute any cleanup tasks defined in its termination process.

Use case 2: List available signal names

Code:

killall --list

Motivation: This use case is used to obtain a list of available signal names. Knowing the available signal names allows you to use specific signals for terminating a process.

Explanation: The ‘–list’ flag is used with the ‘killall’ command to list all available signal names without the ‘SIG’ prefix. These signal names can be used while terminating a process by specifying the desired signal.

Example output: The output will display a list of available signal names, such as TERM, HUP, INT, etc., that can be used with the ‘killall’ command.

Use case 3: Interactively ask for confirmation before termination

Code:

killall -i process_name

Motivation: This use case is used when you want to confirm the termination of a process before it is actually killed. It is helpful to prevent accidental termination of processes.

Explanation: The ‘-i’ flag is used with the ‘killall’ command to interactively ask for confirmation before terminating the process. During execution, the command will prompt the user for confirmation by displaying the process name and asking for ‘y’ (yes) or ’n’ (no) input.

Example output: When executing ‘killall -i process_name’, the command will prompt the user with a confirmation message, displaying the process name. The user can then respond with ‘y’ to confirm termination or ’n’ to cancel the termination.

Use case 4: Terminate a process using the SIGINT signal

Code:

killall -INT process_name

Motivation: This use case is used to terminate a process using the SIGINT signal, which is the equivalent of pressing ‘Ctrl + C’ on the keyboard. It is particularly useful when you want to stop a process gracefully, allowing it to handle the interruption and perform any necessary cleanup actions.

Explanation: The ‘-INT’ flag is used with the ‘killall’ command to send the SIGINT signal to terminate the process. This signal is intercepted by the process, allowing it to exit gracefully and perform any required cleanup tasks.

Example output: The process named ‘process_name’ will receive the SIGINT signal, simulating the action of pressing ‘Ctrl + C’. The process will then handle the interruption and exit gracefully.

Use case 5: Force kill a process

Code:

killall -KILL process_name

Motivation: This use case is used to forcibly kill a process without giving it a chance to handle the termination. It is helpful when a process becomes unresponsive, and graceful termination is not possible.

Explanation: The ‘-KILL’ flag is used with the ‘killall’ command to send the SIGKILL signal to forcefully terminate the process. Unlike other signals, the process cannot intercept or handle this signal, resulting in immediate termination.

Example output: The process named ‘process_name’ will receive the SIGKILL signal and be terminated abruptly without any chance to perform cleanup or save data.

Conclusion:

The ‘killall’ command provides a convenient way to send kill signals to processes by name. With various options for different signals, it allows for both graceful and forced termination of processes. By understanding the different use cases and flags of the ‘killall’ command, you can effectively manage and control processes running on your system.