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# 1  
Old 02-21-2012
Question Unix process states

I am trying to write my own Unix compliant (SUSv4) OS - Just a hobby OS, nothing serious. While going through the standard, I couldn't find any explicit information on process states. What I could find was (excluding the real-time considerations)-

Quote:
# 3.444 Zombie Process
A process that has terminated and that is deleted when its exit status has been reported to another process which is waiting for that process to terminate.

#4.1.4 Scheduling Policy
A scheduling policy affects process or thread ordering:
- When a process or thread is a running thread and it becomes a blocked thread
- When a process or thread is a running thread and it becomes a preempted thread
- When a process or thread is a blocked thread and it becomes a runnable thread
- When a running thread calls a function that can change the priority or scheduling policy of a process or thread
- In other scheduling policy-defined circumstances
From this it can be inferred that the following process states might exist-
RUNNING, BLOCKED, PREEMPTED, RUNNABLE, ZOMBIE

I was wondering whether the Unix specification gives something more detailed?

If not, does any implementation of the above criteria meet the specification? Or is there something more?
# 2  
Old 02-21-2012
From "man ps" , a list of the possible values of the "state" field.

0 Nonexistent
S Sleeping
W Waiting
R Running
I Intermediate
Z Terminated
T Stopped
X Growing


You'll probably find a lot of variation.
# 3  
Old 02-22-2012
@methyl

I understand that there are a lot of variations. I was just wondering if the standard specifies / recommends / hints at any particular model.

The Linux man pages do give the above data. However the ps manual from the SUSv4 doesn't really say anything about process states. Checkout http://pubs.opengroup.org/onlinepubs/9699919799/utilities/ps.html

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