ps (list processes) in Linux CLI - Step-by-Step Execution

Concept Flow - ps (list processes)

Run 'ps' command

↓

System collects process info

↓

Display process list

↓

User reads output or pipes it

The 'ps' command asks the system to gather current process details and then shows them as a list.

Execution Sample

Linux CLI

ps

This command lists the current processes running in the terminal session.

Execution Table

Step	Action	System Response	Output Example
1	User types 'ps' and presses Enter	Shell runs 'ps' command
2	'ps' collects process info for current terminal session	System gathers PID, TTY, TIME, CMD
3	'ps' formats and prints the process list	Output shows columns PID, TTY, TIME, CMD	PID TTY TIME CMD 1234 pts/0 00:00:00 bash 5678 pts/0 00:00:00 ps
4	User reads the list or pipes it for further use	Process list is ready for viewing or scripting
5	No more processes to list, command ends	Shell prompt returns

💡 'ps' finishes after listing current processes and returns control to the shell

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
Process List	empty	collected current session processes	formatted for display	displayed to user
Output	none	none	process info lines	printed on screen

Key Moments - 3 Insights

Why does 'ps' only show processes related to my terminal by default?

By default, 'ps' shows processes attached to your current terminal (TTY). This is why the output is limited, as seen in execution_table step 2 where it collects only current session processes.

What do the columns PID, TTY, TIME, and CMD mean in the output?

PID is the process ID number, TTY is the terminal associated, TIME is CPU time used, and CMD is the command name. This is shown in execution_table step 3 output example.

How can I see all processes, not just mine?

You can use options like 'ps aux' to list all processes. The basic 'ps' command shown here only lists your session's processes, as explained in the concept_flow.

Visual Quiz - 3 Questions

Look at the execution table, what does 'ps' do at step 2?

A Collects process info for current terminal session

B Prints the process list on screen

C Ends the command and returns to shell

D Waits for user input

💡 Hint

Check the 'System Response' column in step 2 of execution_table

At which step does 'ps' display the process list?

A Step 2

B Step 3

C Step 1

D Step 5

💡 Hint

Look at the 'Output Example' column in execution_table

If you want to see all processes, not just your terminal's, what should you do?

A Use 'ps' with no options

B Restart the terminal

C Use 'ps aux' or similar options

D Use 'ps' and then press Enter twice

💡 Hint

Refer to key_moments where it explains how to see all processes

Concept Snapshot

ps command lists processes running in your terminal session
Syntax: ps
Shows columns: PID (process ID), TTY (terminal), TIME (CPU time), CMD (command)
Default shows only your session's processes
Use options like 'ps aux' to see all processes

Full Transcript

The 'ps' command is used to list processes running in your current terminal session. When you type 'ps' and press Enter, the system collects information about processes related to your terminal, including their process ID (PID), terminal (TTY), CPU time used (TIME), and the command name (CMD). This information is then displayed as a list. By default, 'ps' only shows processes attached to your terminal. To see all processes on the system, you can use options like 'ps aux'. The command finishes after printing the list and returns control to the shell prompt.