pcntl_waitpid

(PHP 4 >= 4.1.0, PHP 5, PHP 7)

pcntl_waitpid — Waits on or returns the status of a forked child

설명

int pcntl_waitpid ( int $pid , int &$status [, int $options = 0 ] )

Suspends execution of the current process until a child as specified by the pid argument has exited, or until a signal is delivered whose action is to terminate the current process or to call a signal handling function.

If a child as requested by pid has already exited by the time of the call (a so-called "zombie" process), the function returns immediately. Any system resources used by the child are freed. Please see your system's waitpid(2) man page for specific details as to how waitpid works on your system.

인수

pid

The value of pid can be one of the following:

**possible values for `pid`**
< -1	wait for any child process whose process group ID is equal to the absolute value of `pid`.
-1	wait for any child process; this is the same behaviour that the wait function exhibits.
0	wait for any child process whose process group ID is equal to that of the calling process.
> 0	wait for the child whose process ID is equal to the value of `pid`.

Note:
Specifying -1 as the pid is equivalent to the functionality pcntl_wait() provides (minus options).

status

pcntl_waitpid() will store status information in the status parameter which can be evaluated using the following functions: pcntl_wifexited(), pcntl_wifstopped(), pcntl_wifsignaled(), pcntl_wexitstatus(), pcntl_wtermsig() and pcntl_wstopsig().

options

The value of options is the value of zero or more of the following two global constants OR'ed together:

**possible values for `options`**
WNOHANG	return immediately if no child has exited.
WUNTRACED	return for children which are stopped, and whose status has not been reported.

반환값

pcntl_waitpid() returns the process ID of the child which exited, -1 on error or zero if WNOHANG was used and no child was available

참고

pcntl_fork() - Forks the currently running process
pcntl_signal() - Installs a signal handler
pcntl_wifexited() - Checks if status code represents a normal exit
pcntl_wifstopped() - Checks whether the child process is currently stopped
pcntl_wifsignaled() - Checks whether the status code represents a termination due to a signal
pcntl_wexitstatus() - Returns the return code of a terminated child
pcntl_wtermsig() - Returns the signal which caused the child to terminate
pcntl_wstopsig() - Returns the signal which caused the child to stop

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User Contributed Notes 3 notes

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saguto dot l7cc at gmail dot com ¶

16 years ago


please note, if you using configure option --enable-sigchild(Enable PHP's own SIGCHLD handler) when complie php(under linux 2.6.18-53.1.13.el5.centos.plus and php 5.2.5 as I know), pcntl_waitpid and pcntl_wait in php script would never return the child pid, because the build in handle get it first.

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fx4084 at gmail dot com ¶

10 years ago


<?php
$childs = array();

// Fork some process.
for($i = 0; $i < 10; $i++) {
    $pid = pcntl_fork();
    if($pid == -1)
        die('Could not fork');

    if ($pid) {
        echo "parent \n";
        $childs[] = $pid;
    } else {
        // Sleep $i+1 (s). The child process can get this parameters($i).
        sleep($i+1);
        
        // The child process needed to end the loop.
        exit();
    }
}

while(count($childs) > 0) {
    foreach($childs as $key => $pid) {
        $res = pcntl_waitpid($pid, $status, WNOHANG);
        
        // If the process has already exited
        if($res == -1 || $res > 0)
            unset($childs[$key]);
    }
    
    sleep(1);
}
?>

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-1

renmengyang567 at gmail dot com ¶

5 years ago


<?php

declare(ticks = 1);
function zp_handler($signal) {
    $id = pcntl_waitpid(-1, $status, WNOHANG);
    if (pcntl_wifexited($status)) 
    {
        printf("Removed Chlid id: %d \n",$id);
        printf("Chlid status: %d \n",pcntl_wexitstatus($status));
    }
}

//pcntl_signal_dispatch();
pcntl_signal(SIGCHLD, "zp_handler");
//pcntl_signal_dispatch();
//

$pid = pcntl_fork();
if ($pid == 0)
{
    print "#1 Hi, I'm child process".PHP_EOL;
    sleep(3);
    return 10;
}
else 
{
    print "#1parent process id:".$pid.PHP_EOL;
    $pid = pcntl_fork();
    if ($pid == 0)
    {   print "#2 Hi, I'm child process".PHP_EOL;
        sleep(10);
        exit(20);
    } 
    else 
    {
        print "#2parent process id:".$pid.PHP_EOL;
        for ($i=0; $i <10 ; $i++) { 
            print "wait..".PHP_EOL;
            sleep(10);
        }
    }
}
?>

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