"ps" - Display Current Processes

Linux Apps Tutorials - Herong's Tutorial Examples

∟"ps" - Display Current Processes

This section provides a tutorial example on how to use 'ps' command to display current process on the system.

What Is Process? - A process is a unit of work that is currently running in the operating system. A process has the following basic properties:

PID - A number that identifies the process.
UID - The user ID who owns the process.
Command - The command that initiated the process.
Time - The elapse time since the starting moment of the process.
Priority - A number that indicates the execution priority of the process comparing to other processes.
TTY (or Teletype) - A termainl device attached to the process to handle input and output.

You can use the "ps" command to display current processes and their properties. Here are some examples:

1. Display processes associated with the current terminal session using the "ps" command with default options.

herong$ ps
  PID TTY          TIME CMD
 1171 pts/1    00:00:00 sleep
 1172 pts/1    00:00:00 ps
31723 pts/1    00:00:00 bash

2. Display processes in long format using the "ps -l" command.

herong$ ps -l
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  1195 31723  0  80   0 -  1820 hrtime pts/1    00:00:00 sleep
0 R  1000  1213 31723  0  80   0 - 11191 -      pts/1    00:00:00 ps
0 S  1000 31723 31720  0  80   0 -  6271 -      pts/1    00:00:00 bash

3. Display processes owned by myself or another user using the "ps -u" command.

herong$ ps -u
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
herong     878  0.0  0.0   9800  2624 pts/0    S+   04:37   0:00 less
herong    1344  0.0  0.0  57184  3792 pts/1    R+   05:17   0:00 ps -u
herong    1345  0.0  0.0   9528  2192 pts/1    S+   05:17   0:00 more
herong   29872  0.0  0.0  24700  5372 pts/0    Ss   Aug24   0:00 -bash
herong   31723  0.0  0.0  25084  5704 pts/1    Ss   02:29   0:00 -bash
...

herong$ ps -u joe
...

4. Display all processes on the system in long format using the "ps -el" command:

$ ps -el
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY       TIME CMD
4 S     0     1     0  0  80   0 - 61833 -      ?     00:03:09 systemd
1 S     0     2     0  0  80   0 -     0 -      ?     00:00:01 kthreadd
1 I     0     3     2  0  60 -20 -     0 -      ?     00:00:00 rcu_gp
1 I     0     4     2  0  60 -20 -     0 -      ?     00:00:00 rcu_par_gp
1 I     0     8     2  0  60 -20 -     0 -      ?     00:00:00 mm_percpu_wq
1 S     0     9     2  0  80   0 -     0 -      ?     00:00:00 ksoftirqd/0
1 I     0    10     2  0  80   0 -     0 -      ?     00:02:42 rcu_sched
...