In the Linux environment, process control refers to the ability to manage and manipulate running processes. This is an essential skill for system administrators and Linux users as it allows them to monitor, start, stop, and manipulate processes as needed. Understanding process control is crucial for troubleshooting, resource management, and optimizing system performance.

Linux provides several tools and commands that enable process control. These tools allow users to view running processes, send signals to processes, change process priorities, and manage process groups. By mastering these tools, users can effectively manage and control processes in the Linux environment.

Examples:

1. Viewing Running Processes: To view the list of running processes, you can use the ps command. By default, it displays the processes owned by the current user in a tabular format.

$ ps aux

This command will show detailed information about all running processes, including their process ID (PID), CPU and memory usage, and other details.

2. Sending Signals to Processes: In Linux, you can send signals to processes using the kill command. The most commonly used signal is SIGTERM (termination signal), which gracefully terminates a process.

To send a SIGTERM signal to a process with a specific PID, run the following command:

$ kill PID

You can also send different signals to processes, such as SIGKILL (forceful termination) or SIGSTOP (stop the process execution).

3. Changing Process Priorities: Linux allows you to change the priority of a process using the nice command. The priority value ranges from -20 (highest priority) to 19 (lowest priority). By default, processes have a priority of 0.

To increase the priority of a process, use the following command:

$ nice -n value command

For example, to start a process with a higher priority, you can use:

$ nice -n -10 ./myprocess

4. Managing Process Groups: Process groups in Linux allow you to manage multiple processes as a single entity. The pgrep and pkill commands are useful for working with process groups.

To list all processes in a specific process group, use the pgrep command followed by the process group ID (PGID):

$ pgrep -g PGID

To kill all processes in a process group, you can use the pkill command:

$ pkill -g PGID