10 examples of ps commands

Linux ps command

Linux's ps command is a basic tool for viewing processes run by the system. It provides a snapshot of the current process with specific information, such as the user ID, cpu usage, memory usage, and command name. It does not display data in real time like top or htop. Although it is simpler in terms of functions and outputs, it is still a necessary process management/detection tool for every linux beginner to understand and learn well.

In this article, we will learn the basic usage of ps commands: searching, filtering, and sorting in different ways.

Syntax description

Ps commands have two syntax rules: BSD and UNIX. Linux beginners are often confused and will misunderstand these two styles. Therefore, before proceeding to the next step, let's find some basic information.

Note: "ps aux" is not the same as "ps-aux ". For example, "-u" is used to display User processes, but "u" means to display specific information.

BSD format-BSD syntax options do not have a break, such:

ps aux

UNIX/LINUX format-there is a break before the option of the syntax in linux format, such:

ps -ef

 

It is possible to mix these two syntaxes in linux. For example, "ps ax-f ". However, in this chapter, we mainly discuss the UNIX format syntax.

How to Use the ps command 1. display all processes

The following command displays a list of all processes.

$ ps ax$ ps -ef

Output to "less" Through MPs queues can be paged.

You can use the "u" or "-f" option to display the process details.

$ ps aux$ ps -ef -f

 

Why is my USER Name Not displayed in the USER column, but others such as root and www-data are displayed? For all users (including yours), if the length is greater than 8 characters, the ps will only display your UID rather than the user name.

2. Display User processes

Use the "-u" option followed by the user name to filter processes of the user. Multiple user names can be separated by commas.

$ ps -f -u www-dataUID        PID  PPID  C STIME TTY          TIME CMDwww-data  1329  1328  0 09:32 ?        00:00:00 nginx: worker processwww-data  1330  1328  0 09:32 ?        00:00:00 nginx: worker processwww-data  1332  1328  0 09:32 ?        00:00:00 nginx: worker processwww-data  1377  1372  0 09:32 ?        00:00:00 php-fpm: pool a.localhost                                               www-data  1378  1372  0 09:32 ?        00:00:00 php-fpm: pool a.localhost                                               www-data  4524  2359  0 10:03 ?        00:00:00 /usr/sbin/apache2 -k startwww-data  4527  2359  0 10:03 ?        00:00:00 /usr/sbin/apache2 -k startwww-data  4528  2359  0 10:03 ?        00:00:00 /usr/sbin/apache2 -k start

3. display the process by name or process id

You can search for a process by adding a name or command after the "-C" option.

$ ps -C apache2  PID TTY          TIME CMD 2359 ?        00:00:00 apache2 4524 ?        00:00:00 apache2 4525 ?        00:00:00 apache2...

To display a process by process id, use the "-p" option and use commas to separate multiple process IDs.

$ ps -f -p 3150,7298,6544

"-C" must provide a precise process name, and it cannot be searched by some names or wildcards. To search for the process list more flexibly, The grep command is usually used.

$ ps -ef | grep apache

4. Sort processes by cpu or memory usage

The system administrator usually wants to find out the processes that consume the most memory or CPU. The sorting option sorts the process list based on specific fields or parameters.

You can use '-- sort' to specify multiple fields and use commas to separate them. In addition, fields can be prefixed with '-' or '+' to indicate descending and ascending sorting. There are many options for sorting. You can use the man page to obtain the complete list.

$ ps aux --sort=-pcpu,+pmem

Displays the top five cpu-consuming processes.

$ ps aux --sort=-pcpu | head -5USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMANDroot         1  2.6  0.7  51396  7644 ?        Ss   02:02   0:03 /usr/lib/systemd/systemd --switched-root --system --deserialize 23root      1249  2.6  3.0 355800 30896 tty1     Rsl+ 02:02   0:02 /usr/bin/X -background none :0 vt01 -nolisten tcproot       508  2.4  1.6 248488 16776 ?        Ss   02:02   0:03 /usr/bin/python /usr/sbin/firewalld --noforksilver    1525  2.1  2.3 448568 24392 ?        S    02:03   0:01 /usr/bin/python /usr/share/system-config-printer/applet.py

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