[Sussex] the who/what/why/when of processes ( proc-i ? ;)

[Geoff Teale]

Dunk,

If you're C is upto scratch then this page is a good example.  It starts
with a program that does exactly the same as you PHP script.

http://www-h.eng.cam.ac.uk/help/tpl/unix/fork.html

As far as handling multiple connections is concerned.  Well, this is
something Steve is going to be dealing with in INSIDE so it may be wise to
have a word with him. 

THe simplest approach is to have a parent that forks every time it recieves
a request.  This isn't the most efficient way of doing things however -
starting new processes is quite "heavy" - for this reason a lot of systems
use threads instead (this creates a whole bundle of other problems
especially in the use of shared memory).

Another approach is some sort of pre-emptive process creation.  Some servers
launch processes in waiting so they are ready ahead of requests (thus
servicing the request more quickly).

For a good example of such a program why not take a little look at the
Apache docs, I'm sure somewhere it will discuss they're approach which has
been pretty damn succesful.

One good thing about Posix Forking is that it is the same across all
languages, C/C++, Bash Scripts.. everything.. it always works pretty much
identically.

-- 
Geoff Teale
geoff.teale at claybrook.co.uk
 


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