12-19-2016
Quote:
Originally Posted by
SirSalt
Alright, thank you for clarifying that
---------- Post updated 12-18-16 at 09:20 PM ---------- Previous update was 12-17-16 at 10:28 PM ----------
As I meditated on what you said, I thought of something. In your #3 explanation, would the tty be process "A"? Or would the tty in your example be process "B"? I guess I have a slight and subtle confusion about using "fork" and "forked" in the verb context. When you said "You actually forked a child ("B")", was forking the child a result of calling fork() in process "A", or calling fork() in process "B"? I hope you can see what I'm getting at here. :P
In #3, A calls
fork(). At that point you have processes A and B. Then B calls
fork(). At that point you have processes A, B, and C all running the same instructions. Then B calls
exit() leaving you with processes A and C running. Then C calls
execl() (or another function from the
exec family) to replace the instructions C was running with the instructions needed to run the daemon. At that point you then have A running the code it was running and you have C running your daemon.
Note that since C was a child of B and B exited, A cannot use
wait() to determine whether or not C is still running and cannot retrieve the exit status of C using
wait(). (Grandparents do not become the parents of their children's orphaned children when their children die before their grandchildren.)
This User Gave Thanks to Don Cragun For This Post:
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LEARN ABOUT PHP
pcntl_fork
PCNTL_FORK(3) 1 PCNTL_FORK(3)
pcntl_fork - Forks the currently running process
SYNOPSIS
int pcntl_fork (void )
DESCRIPTION
The pcntl_fork(3) function creates a child process that differs from the parent process only in its PID and PPID. Please see your system's
fork(2) man page for specific details as to how fork works on your system.
RETURN VALUES
On success, the PID of the child process is returned in the parent's thread of execution, and a 0 is returned in the child's thread of
execution. On failure, a -1 will be returned in the parent's context, no child process will be created, and a PHP error is raised.
EXAMPLES
Example #1
pcntl_fork(3) example
<?php
$pid = pcntl_fork();
if ($pid == -1) {
die('could not fork');
} else if ($pid) {
// we are the parent
pcntl_wait($status); //Protect against Zombie children
} else {
// we are the child
}
?>
SEE ALSO
pcntl_waitpid(3), pcntl_signal(3), setproctitle(3).
PHP Documentation Group PCNTL_FORK(3)