Viewing Processes (ps)

The ps command shows information about running processes. It's essential for monitoring what's running on your system.

Basic Usage

ps

Understanding Processes

A process is a running program. Each process has:

• PID: Process ID (unique number)
• PPID: Parent Process ID
• User: Who started it
• State: Running, sleeping, etc.
• Command: The program running

Common ps Options

Command	Description
ps	Your processes in current terminal
ps aux	All processes, detailed
ps -ef	All processes, full format
ps -u user	Processes for specific user

ps aux - The Most Useful Form

ps aux

Column Meanings

Column	Meaning
USER	Process owner
PID	Process ID
%CPU	CPU usage
%MEM	Memory usage
VSZ	Virtual memory size
RSS	Resident set size
TTY	Terminal
STAT	Process state
START	Start time
TIME	CPU time used
COMMAND	Command and arguments

Exercise: View All Processes

Use ps aux to see all running processes:

Process States

The STAT column shows process state:

Code	State
R	Running
S	Sleeping
D	Uninterruptible sleep
T	Stopped
Z	Zombie

Filtering Processes

With grep

ps aux | grep python
ps aux | grep nginx
ps aux | grep -v grep    # Exclude grep itself

For Specific User

ps -u root
ps -u $(whoami)

Useful ps Commands

Tree View

ps auxf          # Forest format (shows hierarchy)
pstree           # Process tree

By Memory/CPU

ps aux --sort=-%mem | head    # Top memory users
ps aux --sort=-%cpu | head    # Top CPU users

Custom Columns

ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem

Exercise: Find a Specific Process

Find all bash processes:

ps vs top

Feature	ps	top
Output	Snapshot	Real-time
Interactive	No	Yes
Best for	Scripting	Monitoring

Key Takeaways

• ps shows running processes
• Use ps aux for all processes with details
• Filter with grep to find specific processes
• PID is the unique process identifier
• STAT shows process state (Running, Sleeping, etc.)