There are three common ways to view running processes in Linux systems: 1. Use the ps command to view static process information, such as ps, ps aux and ps -ef to display processes of different ranges; 2. Use top or htop to monitor process status in real time, and support sorting by CPU or memory usage; 3. Use the /proc file system to deeply view the underlying details of the process, such as cmdline, environment, maps and other files. These methods are suitable for daily viewing, real-time monitoring and advanced debugging scenarios respectively.

Viewing running processes in Linux systems is the basic operation of daily system management and problem investigation. Mastering several commonly used methods can help you quickly understand the system status and locate programs with high resource occupancy.

Use the ps command to view the process

ps is the most basic command to view processes. It can be run directly in the terminal, suitable for script calls or quick viewing of the current user's processes.

Commonly used combination commands are as follows:

• ps : Only display processes related to the current terminal.
• ps aux : Displays all processes of all users, and is the first choice for viewing the overall process status of the system.
• ps -ef : also displays all processes, with slightly different formats, and is often used to view the parent-child relationship of processes.

For example, executing ps aux will see the following fields:

• USER: The user running the process
• %CPU and %MEM: CPU and memory usage
• COMMAND: Command to start the process

You can filter specific processes in combination with grep , such as:

 ps aux | grep nginx

Use top to monitor processes in real time

If you want to view process status in real time, top is an interactive tool that continuously refreshes and displays system resources and process information.

The startup method is very simple:

 top

In the interface, you can see:

• Overall CPU and memory usage
• Information on PID, user, CPU/memory usage of each process

Common operations:

• Sort by CPU usage by P
• Sort by memory usage by M
• Press q to exit

If you want a more modern and more powerful alternative, try htop , which supports mouse operation and color highlighting, but may require additional installation.

Use the /proc file system to view process details

Linux stores process information in the /proc directory as a file. Each running process has a subdirectory named after PID, which contains the detailed information of the process.

For example, view process information with PID 1:

 cat /proc/1/status

You can find it in /proc/<pid>/</pid> :

• cmdline : Start the command
• environ : environment variable
• maps : memory map
• fd/ : Open file descriptor

This method is suitable for advanced users to debug or use in scripts, and can obtain more underlying information than ps and top .

Basically these are the methods. Different tools can be selected in different scenarios: use ps for daily viewing, use top or htop for real-time monitoring, and use /proc for in-depth debugging. These commands are not complicated, but they are very practical, and can greatly improve the investigation efficiency after mastering them.

The above is the detailed content of How to see the running processes in Linux?. For more information, please follow other related articles on the PHP Chinese website!