Listing Active Processes with PS and TOP in Linux.

To see which processes are currently on a system, most people use the “ps” and “top” commands. The “ps” command gives you a snapshot (in a single list) of processes running at the moment. The “top” command offers a screen oriented, constantly updated listing of running commands, sorted as you choose ( by CPU, memory, UID, etc).

ps #List processes of current user at current shell

root@ubuntu-box:~# ps
  PID TTY          TIME CMD
 2988 pts/0    00:00:00 su
 2996 pts/0    00:00:00 bash
 3047 pts/0    00:00:00 ps

ps -u jorge #Show all jorge’s running processes

root@ubuntu-box:~# ps -u jorge
  PID TTY          TIME CMD
 2662 ?        00:00:00 x-session-manag
 2725 ?        00:00:00 VBoxClient
 2730 ?        00:00:00 VBoxClient
 2737 ?        00:00:00 VBoxClient
 2748 ?        00:00:00 ssh-agent

ps -u jorge u #Show all running processes with CPU/MEM

root@ubuntu-box:~# ps -u jorge u
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
jorge     2662  0.1  1.3  26392  7100 ?        Ssl  02:17   0:00 x-session-manag
jorge     2725  0.1  0.3   5736  1772 ?        Sl   02:17   0:00 /usr/bin/VBoxCl
jorge     2730  0.0  0.2   5608  1148 ?        Sl   02:17   0:00 /usr/bin/VBoxCl
jorge     2737  0.0  0.2   5608  1196 ?        Sl   02:17   0:00 /usr/bin/VBoxCl
jorge     2748  0.0  0.1   4784   600 ?        Ss   02:17   0:00 /usr/bin/ssh-ag

ps -e #show every running process

root@ubuntu-box:~# ps -e
  PID TTY          TIME CMD
    1 ?        00:00:00 init
    2 ?        00:00:00 kthreadd
    3 ?        00:00:00 migration/0
    4 ?        00:00:00 ksoftirqd/0
    5 ?        00:00:00 watchdog/0

ps aux #show every running process BSD style

 root@ubuntu-box:~# ps aux
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.2  0.3   3084  1888 ?        Ss   02:17   0:00 /sbin/init
root         2  0.0  0.0      0     0 ?        S<   02:17   0:00 [kthreadd]
root         3  0.0  0.0      0     0 ?        S<   02:17   0:00 [migration/0]
root         4  0.0  0.0      0     0 ?        S<   02:17   0:00 [ksoftirqd/0]

ps -ef –forest #show process hierarchy in forest format

root@ubuntu-box:~# ps -ef --forest
UID        PID  PPID  C STIME TTY          TIME CMD
111       2139     1  0 02:17 ?        00:00:00 /usr/sbin/hald
root      2205  2139  0 02:17 ?        00:00:00  \_ hald-runner
root      2235  2205  0 02:17 ?        00:00:00      \_ hald-addon-input: Listening on
root      2271  2205  0 02:17 ?        00:00:00      \_ hald-addon-storage: polling /de
root      2272  2205  0 02:17 ?        00:00:00      \_ hald-addon-storage: no polling
111       2276  2205  0 02:17 ?        00:00:00      \_ hald-addon-acpi: listening on

ps -C sshd #display running sshd process

root@ubuntu-box:~# ps -C sshd
  PID TTY          TIME CMD
 2103 ?        00:00:00 sshd

or this method using “grep” give the same result
ps -e | grep sshd #display running sshd process

root@ubuntu-box:~# ps -e | grep sshd
 2103 ?        00:00:00 sshd

Now if you want to see process running in your system live, you can use the “top” command.
Here are some examples:

top -d 5 #changes update delay to 5 seconds instead of 3 (default)
top -u username #only display processes for that user
top -p 223, 5632 #only display processes 223, 5632

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