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pcntl_wexitstatus pcntl_wait

Last updated: Fri, 26 Jan 2007

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# pcntl_waitpid

(PHP 4 >= 4.1.0, PHP 5)

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

## Description

int pcntl_waitpid ( int pid, int &status [, int options] )

The pcntl_waitpid() function 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.

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

The value of `pid` can be one of the following:

Таблица 1. 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`.

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

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().

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

Таблица 2. 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.

See also pcntl_fork(), pcntl_signal(), pcntl_wifexited(), pcntl_wifstopped(), pcntl_wifsignaled(), pcntl_wexitstatus(), pcntl_wtermsig() and pcntl_wstopsig().

add a note User Contributed Notes
pcntl_waitpid
Kevin
10-May-2006 03:40
`---
while ($i < intval($argv[1]))
{
$pid = pcntl_fork();
if ($pid == -1)
{
die('could not fork');
}
else
{
if ($pid) // parent
{
$pid_arr[$i] = $pid;
}
else // child
{
performSomeFunction($i+1);
}
}
$i++;
}
---
careful, this will create a lot more children than you probably expect. You must return or exit after performSomeFunction($i+1); ie,
else // child
{
performSomeFunction($i+1);
exit(0);
}`
admin at albert dot us dot com
06-Mar-2006 10:48
`Here's a decent example of the pcntl_waitpid() call:
$i = 0;
$starttime = microtime(TRUE);
$pid_arr = array();
while ($i < intval($argv[1]))
{
$pid = pcntl_fork();
if ($pid == -1)
{
die('could not fork');
}
else
{
if ($pid) // parent
{
$pid_arr[$i] = $pid;
}
else // child
{
performSomeFunction($i+1);
}
}
$i++;
}
foreach ($pid_arr as $pid)
{
// we are the parent
pcntl_waitpid($pid, $status);
}
$elapsed = microtime(TRUE) - $starttime;
print "\n==> total elapsed: " . sprintf("%f secs.\n", $elapsed);`
add a note
pcntl_wexitstatus pcntl_wait

Last updated: Fri, 26 Jan 2007
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