Linux ps Command
The Linux ps (short for "process status") command is used to display the status of the current processes, similar to the Task Manager in Windows.
Syntax
ps [options] [--help]
Parameters:
The ps command has many parameters, here are some commonly used ones with brief explanations:
-A: Lists all processes
-w: Displays in a wider format to show more information
-au: Shows more detailed information
-aux: Shows all processes including those owned by other users
The au(x) output format:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
USER: Process owner
PID: Process ID
%CPU: CPU usage percentage
%MEM: Memory usage percentage
VSZ: Virtual memory size
RSS: Resident Set Size (memory size)
TTY: Terminal's minor device number
STAT: Process status:
D: Uninterruptible sleep (usually IO)
R: Running
S: Sleeping
T: Stopped
Z: Zombie (defunct but temporarily not removable)
W: Paging (not valid since the 2.6 kernel)
<: High-priority process
N: Low-priority process
L: Has pages locked into memory (for real-time and custom IO)
START: Process start time
TIME: Execution time
COMMAND: Command executed
Examples
To find a specific process:
ps -ef | grep process_keyword
For example, to display PHP processes:
# ps -ef | grep php
root 794 1 0 2020 ? 00:00:52 php-fpm: master process (/etc/php/7.3/fpm/php-fpm.conf)
www-data 951 794 0 2020 ? 00:24:15 php-fpm: pool www
www-data 953 794 0 2020 ? 00:24:14 php-fpm: pool www
www-data 954 794 0 2020 ? 00:24:29 php-fpm: pool www
...
To display process information:
# ps -A
PID TTY TIME CMD
1 ? 00:00:02 init
2 ? 00:00:00 kthreadd
3 ? 00:00:00 migration/0
4 ? 00:00:00 ksoftirqd/0
5 ? 00:00:00 watchdog/0
6 ? 00:00:00 events/0
7 ? 00:00:00 cpuset
8 ? 00:00:00 khelper
9 ? 00:00:00 netns
10 ? 00:00:00 async/mgr
11 ? 00:00:00 pm
12 ? 00:00:00 sync_supers
13 ? 00:00:00 bdi-default
14 ? 00:00:00 kintegrityd/0
15 ? 00:00:02 kblockd/0
16 ? 00:00:00 kacpid
17 ? 00:00:00 kacpi_notify
18 ? 00:00:00 kacpi_hotplug
19 ? 00:00:27 ata/0
……omitted part of the results
30749 pts/0 00:00:15 gedit
30886 ? 00:01:10 qtcreator.bin
30894 ? 00:00:00 qtcreator.bin
31160 ? 00:00:00 dhclient
31211 ? 00:00:00 aptd
31302 ? 00:00:00 sshd
31374 pts/2 00:00:00 bash
31396 pts/2 00:00:00 ps
To display information for a specific user:
# ps -u root //Display root user process information
PID TTY TIME CMD
1 ? 00:00:02 init
2 ? 00:00:00 kthreadd
3 ? 00:00:00 migration/0
4 ? 00:00:00 ksoftirqd/0
5 ? 00:00:00 watchdog/0
6 ? 00:00:00 events/0
7 ? 00:00:00 cpuset
8 ? 00:00:00 khelper
9 ? 00:00:00 netns
10 ? 00:00:00 async/mgr
11 ? 00:00:00 pm
12 ? 00:00:00 sync_supers
13 ? 00:00:00 bdi-default
14 ? 00:00:00 kintegrityd/0
15 ? 00:00:02 kblockd/0
16 ? 00:00:00 kacpid
...omitted part of the results
30487 ? 00:00:06 gnome-terminal
30488 ? 00:00:00 gnome-pty-helper
30489 pts/0 00:00:00 bash
30670 ? 00:00:00 debconf-communicator
30749 pts/0 00:00:15 gedit
30886 ? 00:01:10 qtcreator.bin
30894 ? 00:00:00 qtcreator.bin
31160 ? 00:00:00 dhclient
31211 ? 00:00:00 aptd
31302 ? 00:00:00 sshd
31374 pts/2 00:00:00 bash
31397 pts/2 00:00:00 ps
Display all process information, including command lines
ps -ef //Display all commands, including command lines
UID PID PPID C STIME TTY TIME CMD root 1 0 0 10:22 ? 00:00:02 /sbin/init root 2 0 0 10:22 ? 00:00:00 [kthreadd] root 3 2 0 10:22 ? 00:00:00 [migration/0] root 4 2 0 10:22 ? 00:00:00 [ksoftirqd/0] root 5 2 0 10:22 ? 00:00:00 [watchdog/0] root 6 2 0 10:22 ? /usr/lib/NetworkManager ...omitted part of the results root 31302 2095 0 17:42 ? 00:00:00 sshd: root@pts/2 root 31374 31302 0 17:42 pts/2 00:00:00 -bash root 31400 1 0 17:46 ? 00:00:00 /usr/bin/python /usr/sbin/aptd root 31407 31374 0 17:48 pts/2 00:00:00 ps -ef ```