list all running processes linux with code examples

There are several ways to list all running processes in Linux, each with its own set of options and capabilities. In this article, we will discuss some of the most commonly used commands for listing processes in Linux and provide code examples for each.

1. ps command

The ps command is one of the most basic and widely used commands for listing processes in Linux. It provides a snapshot of the current processes on the system, including the process ID (PID), the user that owns the process, and the command that started the process.

To list all running processes on the system, you can use the ps -ef command. This command will display all processes, including those that are owned by other users.

$ ps -ef

You can also use ps aux command to list all process with more detailed information like CPU and memory usage.

$ ps aux

2. top command

The top command is another widely used command for listing processes in Linux. It provides a real-time, scrolling view of the processes running on the system, and includes information such as the process ID, user, CPU usage, and memory usage.

To list all running processes using top command, you can use the following command:

$ top

You can also sort the processes based on various criteria like CPU usage, memory usage, process id and more.

$ top -o %CPU

3. htop command

htop is an interactive process viewer for Linux. It is similar to the top command, but it provides a more user-friendly interface and additional functionality.

To list all running processes using htop command, you can use the following command:

$ htop

Like top, htop also provides the ability to sort processes based on various criteria.

$ htop -u <username>

4. lsof command

The lsof command stands for "list open files," and it can be used to list all processes that have a specific file or network socket open. This can be useful for troubleshooting issues related to file or network access.

To list all processes that have a specific file open, you can use the following command:

$ lsof <file>

To list all processes that have a specific network socket open, you can use the following command:

$ lsof -i <protocol>:<port>

5. pgrep and pkill command

pgrep command is used to search for processes by name and display their process IDs. pkill command is used to signal processes based on their name.

To list all processes with the name 'firefox', you can use the following command:

$ pgrep firefox

To send the terminate signal to all processes with the name 'firefox', you can use the following command:

$ pkill firefox

In conclusion, the commands discussed in this article are some of the most commonly used commands for listing processes in Linux. Each command has its own set of options and capabilities, so it is important to understand the capabilities of each command before using it. Additionally, these commands can be combined with other Linux commands and scripts to automate process management tasks.

1. kill command

The kill command is used to send a signal to a process to terminate it. The signal can be specified using the signal name or number, and the default signal is SIGTERM (15).

To terminate a process with the process ID of 1234, you can use the following command:

$ kill 1234

You can also use the -s option to specify the signal, for example to use SIGKILL (9) signal which forcefully terminate the process:

$ kill -s SIGKILL 1234

2. pstree command

The pstree command is used to display a tree of processes on the system, showing the parent-child relationships between processes. This can be useful for understanding the relationship between processes and identifying potential issues with process hierarchy.

To display a tree of all processes on the system, you can use the following command:

$ pstree

You can also use the -p option to display the process ID along with each process name, or the -h option to display the process hierarchy in a more compact format.

3. systemctl command

systemctl is a command-line tool that can be used to manage systemd units. It can be used to start, stop, enable, or disable services, as well as check the status of a service.

To start a service named 'nginx', you can use the following command:

$ systemctl start nginx

To check the status of a service named 'nginx', you can use the following command:

$ systemctl status nginx

To stop a service named 'nginx', you can use the following command:

$ systemctl stop nginx

To enable a service so that it starts automatically at boot time, you can use the following command:

$ systemctl enable nginx

4. systemd-cgtop command

systemd-cgtop is a command line tool that can be used to display a real-time, scrolling view of control groups on the system. Control groups, or cgroups, are a Linux kernel feature that allow processes to be grouped together and managed as a unit.

To display a real-time, scrolling view of control groups on the system, you can use the following command:

$ systemd-cgtop

You can also use the -n option to limit the number of processes displayed, or the --sort-weight option to sort the control groups by a specific metric such as CPU usage or memory usage.

In summary, these commands are useful to manage and monitor processes on Linux systems. Understanding the capabilities of each command and how they can be used in combination with other commands can help you manage processes more effectively and efficiently.

Popular questions

1. What command can be used to list all running processes on a Linux system?
   Answer: The ps -ef command can be used to list all running processes on a Linux system.

2. How can you sort the processes displayed by the top command based on CPU usage?
   Answer: You can use the command top -o %CPU to sort the processes displayed by the top command based on CPU usage.

3. What command can be used to display a tree of processes on the system, showing the parent-child relationships between processes?
   Answer: The pstree command can be used to display a tree of processes on the system, showing the parent-child relationships between processes.

4. How can you start a service named 'nginx' using the systemctl command?
   Answer: The command systemctl start nginx can be used to start a service named 'nginx' using the systemctl command.

5. What command can be used to display a real-time, scrolling view of control groups on the system?
   Answer: The systemd-cgtop command can be used to display a real-time, scrolling view of control groups on the system.

Tag

Processes