Show all running processes in Linux

Q. How do I see all running process in Linux?

A. Both Linux and UNIX support same command to display information about all running process.

ps command gives a snapshot of the current processes. If you want a repetitive update of this status, use top command.

Task: Use ps command

Type the following ps command to display all running process
# ps aux | less

Where,

• -A: select all processes
• a: select all processes on a terminal, including those of other users
• x: select processes without controlling ttys

Task: see every process on the system

# ps -A
# ps -e


Task: See every process except those running as root

# ps -U root -u root -N

Task: See process run by user vivek

# ps -u vivek

Task: Use top command

The top program provides a dynamic real-time view of a running system. Type the top at command prompt:
# top
Output:

To quite press q for help press h.

Task: display a tree of processes

pstree shows running processes as a tree. The tree is rooted at either pid or init if pid is omitted. If a user name is specified, all process trees rooted at processes owned by that user are shown.
$ pstreeOutput:

Task: Lookup process

Use pgrep command. pgrep looks through the currently running processes and lists the process IDs which matches the selection criteria to screen. For example display firefox process id:
$ pgrep firefox

Following command will list the process called sshd which is owned by root user.
$ pgrep -u root sshd

Say hello to htop

htop is interactive process viewer just like top, but allows to scroll the list vertically and horizontally to see all processes and their full command lines. Tasks related to processes (killing, renicing) can be done without entering their PIDs. To install htop type command:
# apt-get install htop
or
# yum install htop
Now type htop to run the command:
# htop

(click to enlarge)

See also:

• Kill process in Linux or terminate a process in UNIX or Linux systems