How to list processes by user and group in Linux

In Linux environments with multiple users and long‑running services, understanding which processes belong to which accounts is essential for troubleshooting and capacity planning. Focusing output on a specific user or group makes it easier to spot runaway tasks, stuck daemons, or resource‑heavy applications without scrolling through the entire process table.

Each process is tagged with real and effective user and group identifiers, and common utilities such as ps, pgrep, and top can filter on these attributes. Options like -u and -U select processes based on usernames or user IDs, while -g and -G narrow results to particular groups or process group leaders to match exactly the context being investigated.

Security settings on some distributions restrict how much detail is visible for processes owned by other users, and inspecting system‑wide activity often requires elevated privileges. Using the correct selectors avoids accidentally hiding important processes and helps keep focus on the accounts or groups that matter, especially when working on remote servers or shared Linux systems.

1. Show processes for a single user with the ps command using both real and effective user selectors.

   $ ps -u user -U user
       PID TTY          TIME CMD
       781 ?        00:00:00 sleep
       782 ?        00:00:00 sleep

   The -u option lists processes for a specific user by username, while -U filters by real user ID.

   -U      Display the processes belonging to the specified real user IDs.
   -u      Display the processes belonging to the specified usernames.

   user is a real user and group name in the system.

   $ id
   uid=1001(user) gid=1001(user) groups=1001(user)

2. Show processes for a single group with the ps command using group selectors.

   $ ps -g user -G user
       PID TTY          TIME CMD
       778 ?        00:00:00 sudo
       779 ?        00:00:00 sudo
       781 ?        00:00:00 sleep
       782 ?        00:00:00 sleep

   The -g option selects by session or process group leader, and -G selects by real group ID or group name.

   -G      Display information about processes which are running with the specified real group IDs.
   -g      Display information about processes with the specified process group leaders.

3. List processes for multiple users at once with the ps command.

   $ ps -u user,root -U user,root
       PID TTY          TIME CMD
         1 ?        00:00:00 systemd
        24 ?        00:00:00 systemd-journal
        64 ?        00:00:00 systemd-udevd
       129 ?        00:00:00 cron
       138 ?        00:00:00 systemd-logind
       147 tty1     00:00:00 agetty
       778 ?        00:00:00 sudo
       779 ?        00:00:00 sudo
       780 ?        00:00:00 sudo
       781 ?        00:00:00 sleep
   ##### snipped #####

   Multiple usernames or IDs can be provided as comma‑separated lists to combine filters for -u, -U, -g, and -G.

4. Filter the ps process list by name or user with the grep command.

   $ ps -aef | grep avahi
   root         780       1  0 21:54 ?        00:00:00 sudo -u avahi bash -lc exec -a avahi-daemon sleep 300
   avahi        783     780  0 21:54 ?        00:00:00 avahi-daemon 300
   root         812       0  0 21:54 pts/2    00:00:00 bash -lc ps -aef | grep avahi
   root         821     812  0 21:54 pts/2    00:00:00 grep avahi

   The grep command filters process output by keyword, which can be a username, group name, or process name.

5. Show processes for a specific user interactively with the top command.

   $ top -u user
   
   top - 21:55:00 up 1 day, 23:23,  0 user,  load average: 0.44, 0.48, 0.55
   Tasks:  17 total,   1 running,  16 sleeping,   0 stopped,   0 zombie
   %Cpu(s):  0.0 us,  0.0 sy,  0.0 ni, 99.1 id,  0.0 wa,  0.0 hi,  0.9 si,  0.0 st
   MiB Mem :   7836.8 total,   1473.1 free,   1623.1 used,   4944.0 buff/cache
   MiB Swap:   1024.0 total,   1024.0 free,      0.0 used.   6213.6 avail Mem
   
       PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
       781 user      20   0    5688   1760   1660 S   0.0   0.0   0:00.00 sleep
       782 user      20   0    5688   1756   1660 S   0.0   0.0   0:00.00 sleep
   ##### snipped #####

   The top command provides real‑time monitoring of CPU and memory usage for processes owned by the specified user.

   top accepts either -u or -U, but not both at the same time, and combining them results in a selection error.

   $ top -u user -U user
   top: conflicting process selections (U/p/u)

6. Display processes for a user using pgrep and include process names in the output.

   $ pgrep -l -u user -U user
   781 sleep
   782 sleep

   The pgrep command lists process IDs filtered by user or group, and the -l flag adds the associated process names to the output.