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Full Discussion: Fork
Top Forums UNIX for Dummies Questions & Answers Fork Post 1632 by Neo on Tuesday 20th of March 2001 06:24:47 PM
Old 03-20-2001
"To Fork" is like "a fork in your path" when you are walking in the forest. The concept is similar in UNIX processes, however the fork occurs with the logic flow of the program and processes.

Consider that your process is running as process ID 100. The process has an open file descriptor listening for incoming TCP/IP connections. When an incoming connection occurs, the process could "fork" another process to handle the incoming connection. The process ID, for example, of the new process that was "forked" could be 132 (whatever the next available process ID was).

When a new process is forked it has a few interesting options. One is to take the content of the global variables and other data structures and make a copies in the new fork. Another option is to fork and completely replace the original process.

So, forking is just something that occurs to a process in its "path of execution". The main difference between forking processes and your fork as your walk down the road is that you can't physically walk down two paths. Software processes can and do spawn many processes by forking.

Hope this helps.

[Edited by Neo on 03-20-2001 at 06:27 PM]
This User Gave Thanks to Neo For This Post:
shekhar_4_u
 

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LEARN ABOUT SUSE

net::server::fork

Net::Server::Fork(3)					User Contributed Perl Documentation				      Net::Server::Fork(3)

NAME

       Net::Server::Fork - Net::Server personality

SYNOPSIS

	 use Net::Server::Fork;
	 @ISA = qw(Net::Server::Fork);

	 sub process_request {
	    #...code...
	 }

	 __PACKAGE__->run();

DESCRIPTION

       Please read the pod on Net::Server first.  This module is a personality, or extension, or sub class, of the Net::Server module.

       This personality binds to one or more ports and then waits for a client connection.  When a connection is received, the server forks a
       child.  The child handles the request and then closes.

       With the exception of parent/child signaling, this module will work (with basic functionality) on Win32 systems.

ARGUMENTS

       check_for_dead
	   Number of seconds to wait before looking for dead children.	This only takes place if the maximum number of child processes
	   (max_servers) has been reached.  Default is 60 seconds.

       max_servers
	   The maximum number of children to fork.  The server will not accept connections until there are free children. Default is 256 children.

       max_dequeue
	   The maximum number of dequeue processes to start.  If a value of zero or undef is given, no dequeue processes will be started.  The
	   number of running dequeue processes will be checked by the check_for_dead variable.

       check_for_dequeue
	   Seconds to wait before forking off a dequeue process.  It is intended to use the dequeue process to take care of items such as mail
	   queues.  If a value of undef is given, no dequeue processes will be started.

CONFIGURATION FILE

       See Net::Server.

PROCESS FLOW

       Process flow follows Net::Server until the post_accept phase.  At this point a child is forked.	The parent is immediately able to wait for
       another request.  The child handles the request and then exits.

HOOKS

       The Fork server has the following hooks in addition to the hooks provided by the Net::Server base class.  See Net::Server

       "$self->pre_accept_hook()"
	   This hook occurs just before the accept is called.

       "$self->pre_fork_hook()"
	   This hook occurs just after accept but before the fork.

       "$self->post_accept_hook()"
	   This hook occurs in the child after the accept and fork.

       "$self->run_dequeue()"
	   This hook only gets called in conjuction with the check_for_dequeue setting.

TO DO

       See Net::Server

AUTHOR

       Paul Seamons <paul@seamons.com>

       Rob Brown <bbb@cpan.org>

SEE ALSO

       Please see also Net::Server::INET, Net::Server::PreFork, Net::Server::MultiType, Net::Server::SIG Net::Server::Single

perl v5.12.1							    2007-02-03						      Net::Server::Fork(3)
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