Question About Multi-Processed Applications... fork()


 
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# 1  
Old 11-19-2008
Question About Multi-Processed Applications... fork()

Assume we have an application built on *nix that uses fork()...then the processes procedure is going to act as follow:

X is considered a parent process (first click on application)
Y is considered a child process of X (second click on application)
Z is considered a child process of Y (third click on application)

If Y terminates, signal is sent to X to let X knows that Y is exited...
If Z terminates, signal is sent to Y (parent process of Z) to let Y knows that Z is exited...

1. Right?

2. If yes, then why Z exits status is not returned to X? Why not all exit status get returned to the very first parent process?
# 2  
Old 11-19-2008
The very first parent process is not your program, it's init, the startup program UNIX runs on boot to create all other processses. I doubt you want your signals to end up there. Smilie Though if the parent dies before the child does, that is where the child's signal will end up.
# 3  
Old 11-19-2008
ha ok, i see. orphan child signal will end up to init....

so it goes like

init()
X
y
Z

X is parent of Y. X is child of init().....

So lets say i opened a browser in *nix. This browser is multi-process.
First browser opened (X) is going to be a child on init()
Second browser (Y) opened, is going to be a child of (X).
X will take care of Y. If X dies, init() takes care of Y..

I hope this is right. I would like somebody to confirm!

Many THANKS!!!
# 4  
Old 11-19-2008
If you open two browsers, they'd be two children of the same parent, not one as the parent of the other.

There's also more layers than init -> user application -> children, though that's enough for examples. Init creates the window server which creates the login manager which creates everything you run; or for a shell, init creates the login shell which creates your processes.
# 5  
Old 11-19-2008
I see...

I made my assumption based on this quote:

"Every process has one parent process. Parent process always has many child processes. and every child process can create another new child process which makes the first child process becomes a parent to the new child process, and in the same time it is considered a child process to its parent process. It is like a parent creates a child and child creates a new child! so the new child process has a parent of a child process who got another parent. It goes like a chain. Parent process does not *always* have many child process only when it forks them."

Thats why i thought second browser is a child of the first browser...
# 6  
Old 11-19-2008
That paragraph isn't written very clearly. If a process created a process, the old process is that new process' parent, it's that simple.
# 7  
Old 11-19-2008
alright....thanks! i got it
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