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ps command

ps - report a snapshot of the current processes.​

The ps command in Linux is a utility used to display information about running processes on your system. It’s essential for monitoring system activity, troubleshooting, or finding process IDs (PIDs) to manage tasks.

Usage: ps [options]

  • options: Flags that control what processes to show and how to display them.

  • No options shows minimal info about your current shell’s processes.

    Common Options

    OptionDescription
    -eShow all processes
    -fFull-format listing
    -uFilter by user
    -oCustom output columns
    auxBSD-style detailed list (no dash)
    -pShow specific PID (e.g., -p 1234)

Examples​

  • Basic Usage

    Run ps without options to see processes tied to your current terminal.

    ps
    • Output (example): 
        PID TTY          TIME CMD
      1234 pts/0    00:00:00 bash
      5678 pts/0    00:00:00 ps
    • Explanation:
      • PID: Process ID.
      • TTY: Terminal associated with the process.
      • TIME: CPU time used.
      • CMD: Command that started the process.

  • Showing All Processes

    Use -e (everything) or -A to list all running processes on the system.

    ps -e
    • Output (partial): 
        PID TTY          TIME CMD
          1 ?        00:00:01 systemd
          2 ?        00:00:00 kthreadd
        123 ?        00:00:00 sshd

  • Adding More Details

    Use -f (full-format) for more columns like user, parent PID, and start time.

    ps -ef
    • Output (partial): 
      UID        PID  PPID  C STIME TTY          TIME CMD
      root         1     0  0 10:00 ?        00:00:01 /sbin/init
      root       123    1  0 10:01 ?        00:00:00 /usr/sbin/sshd
      alice     4567  123  0 10:02 pts/0    00:00:00 bash
    • Explanation:
      • UID: User running the process.
      • PPID: Parent process ID.
      • C: CPU usage percentage.
      • STIME: Start time.

  • Customizing Output

    Use -o (output format) to select specific columns.

    ps -eo pid,user,cmd
    • Output: 
        PID USER     CMD
          1 root     /sbin/init
        123 root     /usr/sbin/sshd
      4567 alice    bash
    • Common fields: pid, user, cmd, pcpu (CPU %), pmem (memory %).

  • Filtering by User

    Use -u to show processes for a specific user.

    ps -u alice
    • Output: 
        PID TTY          TIME CMD
      4567 pts/0    00:00:00 bash
      4589 pts/0    00:00:01 vim

  • Process Tree View

    Use aux (BSD-style) with ps for a detailed, user-friendly list, often paired with grep.

    ps aux
    • Output (partial): 
      USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
      root         1  0.0  0.1 123456  7890 ?        Ss   10:00   0:01 /sbin/init
      alice     4567  0.0  0.2 234567 12345 pts/0    Ss   10:02   0:00 bash
    • Explanation:
      • %CPU, %MEM: Resource usage.
      • VSZ, RSS: Virtual and resident memory.
      • STAT: Process state (e.g., S = sleeping, R = running).

    Filter with grep:

    ps aux | grep firefox
    • Finds Firefox processes.

To get help related to the ps command use --help option​

ps --help

Usage:
 ps [options]

 Try 'ps --help <simple|list|output|threads|misc|all>'
  or 'ps --help <s|l|o|t|m|a>'
 for additional help text.

For more details, check the manual with man ps

Last updated on by AB