How To Check Linux List Processes

Prerequisites

Before checking processes on your Linux system, ensure you have:

• A Linux distribution installed on your machine.
• Access to a terminal or command-line interface.
• Basic understanding of navigating the terminal.

Understanding Linux Processes

A process represents a running instance of a program or command on your system.

Each application you open creates at least one process. For example, launching a web browser initiates a process that continues until you close the application.

Commands executed in the terminal also generate processes. These terminate once the command completes or you stop it manually.

How to Check Linux List Processes Using the ps Command

Use the ps command to display currently running processes. This command shows process status information in real-time.

Run the basic command:

$ ps

This displays processes for your current shell with four columns:

• PID shows the unique process identifier.
• TTY indicates the terminal type.
• TIME displays total CPU usage.
• CMD shows the command that started the process.

View all running processes with detailed information:

$ ps aux

The a option displays processes from all users. The u option shows user-oriented format. The x option includes processes without a terminal.

This command outputs eleven columns:

• USER identifies the process owner.
• PID provides the process ID.
• %CPU shows CPU usage percentage.
• %MEM displays memory usage percentage.
• VSZ indicates virtual memory size in kilobytes.
• RSS shows resident set size.
• TTY displays the controlling terminal.
• STAT reveals process state.
• START shows when the process started.
• TIME displays CPU time used.
• COMMAND shows the full command.

How to Check Linux List Processes Using the top Command

The top command provides a dynamic real-time view of running processes.

Launch the command:

$ top

This displays processes sorted by resource usage. The interface updates automatically every three seconds by default.

Key information includes:

• PID for process identification.
• USER showing who runs the process.
• PR indicating scheduling priority.
• NI displaying nice value.
• VIRT showing virtual memory usage.
• RES indicating physical memory usage.
• S revealing process status (running, sleeping, idle).
• %CPU showing CPU consumption.
• %MEM displaying memory usage.
• COMMAND showing the process name.

Press q to exit the top interface.

How to Check Linux List Processes Using the htop Command

The htop command offers an enhanced interactive interface compared to top.

Install htop if not already available:

$ sudo apt update && sudo apt install htop

For Red Hat-based systems:

$ sudo yum install htop

Launch htop:

$ htop

This displays a color-coded interface with processes sorted by CPU usage. You can scroll through the list, search for specific processes, and manage them interactively.

The interface includes mouse support for easier navigation. You can click on processes to select them and use keyboard shortcuts for management tasks.

How to Filter Process Lists

Combine commands with pipes to filter results.

Display output one page at a time:

$ ps aux | less

Search for a specific process:

$ ps aux | grep firefox

This returns only lines containing the specified term.

Use pgrep to find process IDs by name:

$ pgrep chrome

This outputs the PID of matching processes without additional details.

How to Terminate Running Processes

Stop a process using its PID:

$ kill 1234

Replace 1234 with the actual process ID.

Force termination with the -9 option:

$ kill -9 1234

Kill processes by name:

$ pkill firefox

This terminates all processes matching the specified name.

Conclusion

Monitoring processes helps maintain system health and troubleshoot performance issues.

The ps command provides snapshots of current processes. The top command offers real-time monitoring. The htop command delivers an interactive interface for easier management.

Combine these tools with grep and pipes to filter results effectively. Use kill commands to terminate unresponsive processes when necessary.

Check the manual pages for each command to explore additional options and capabilities.