🔄 Day 7: Process States

State is just a snapshot of a process at a moment. 📸

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🧊 The 4 Main Process States

State	Name	Description
R	Running	The process is running or ready to run.
S	Sleeping	Waiting for an event or I/O. (Very common).
T	Stopped	Suspended by a signal like SIGSTOP or SIGSTP (Ctrl+Z).
Z	Zombie 🧟	Finished execution but still in the process table.

Zombie Example: A person has passed away, but their official records still show them as "Alive" because the death certificate hasn't been processed. The record exists, but the entity is gone. ☠️

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🔗 States & Signals

Signals change the state of a process. Here is the relationship:

SIGNAL	Effect / New State
SIGINT	Gone (Stopped & Cleared)
SIGTERM	Gone (Polite Stop)
SIGSTP	T (Stopped/Paused)
SIGSTOP	T (Stopped/Paused)
SIGCONT	R or S (Running/Sleeping)
SIGKILL	Gone (Forced Kill)

Note:

• S+: Foreground Sleeping (Process is running in the foreground).
• S: Background Sleeping (Process is running in the background).
• The + sign indicates Foreground processes.

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🎮 Practice Scenarios

1. Open Terminal: Open your terminal in Kali.
2. Split Terminal: Use Ctrl + Shift + R (or your shortcut).
3. Start Process:
   In the left terminal:
   sleep 500
4. Check State:
   In the right terminal:
   ps aux | grep "sleep 500"
   You should see S+ (Sleeping + Foreground).
5. Background It:
   Pause (Ctrl + Z) and send to background (bg).
6. Check State Again:
   Run the ps command again.
   You will now see S (Sleeping, no +).
7. Stop It:
   Send a SIGSTOP to the PID.
8. Final Check:
   Check status again. You should see T (Stopped).

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