PHP Doku:: Sendet einem Prozess ein Signal - function.posix-kill.html

Verlauf / Chronik / History: (1) anzeigen

Sie sind hier:
Doku-StartseitePHP-HandbuchFunktionsreferenzErweiterungen zur ProzesskontrollePOSIXPOSIX Funktionenposix_kill

Ein Service von Reinhard Neidl - Webprogrammierung.

POSIX Funktionen

<<posix_isatty

posix_mkfifo>>

posix_kill

(PHP 4, PHP 5)

posix_killSendet einem Prozess ein Signal

Beschreibung

bool posix_kill ( int $pid , int $sig )

Sendet das Signal sig zum Prozess mit der Prozesskennung pid.

Parameter-Liste

pid

Die Prozesskennung

sig

Eine der PCNTL-Signalkonstanten.

Rückgabewerte

Gibt bei Erfolg TRUE zurück. Im Fehlerfall wird FALSE zurückgegeben.

Siehe auch

  • Die kill(2)-Manpage des POSIX-Systems, die zusätzliche Informationen über negative Prozess-IDs, die speziellen pid 0 und -1 und die Signalnummer 0 enthält.


6 BenutzerBeiträge:
- Beiträge aktualisieren...
Skippy
14.01.2009 11:12
In order to check the outcome of posix_kill() you can use posix_get_last_error(), which will return 0 (zero) in case of success and a non-zero error code otherwise. Use the number returned by posix_get_last_error() as a parameter to posix_strerror() to get a human-readable error message corresponding to that error code.

Please note that a non-zero code from posix_get_last_error() does NOT mean that the pid doesn't exist; it only means that posix_kill() ran into trouble signalling that process. For example, the pid may exist but the process is owned by a user other than the one you use to run the code, and you're not root; in which case you'll get an error saying you're not allowed to signal that process (operation not permitted).

Accordingly, the code posted by Jille earlier is WRONG. According to the POSIX spec (see errno.h on your system), EPERM means "operation not permitted". This should NOT be taken as indication that the pid doesn't exist, it merely means that posix_kill() couldn't signal that process. If anything, it should be a hint that a process with that pid IS running.

errno.h constant names definitions:
http://www.opengroup.org/onlinepubs/009695399/basedefs/errno.h.html

Unfortunately, PHP does not currently define constants with these names (such as EPERM, ENOENT, ESRCH etc.) A non-complete subset is defined for socket operations (SOCKET_EPERM for example), but it doesn't hold all the possible POSIX error constants; ESRCH for instance is of particular interest for posix_kill(), but SOCKET_ESRCH doesn't exist, because it means "no such process" and doesn't make sense for sockets.

Solutions:
* Have PHP devs define these constants in a future PHP version.
* Look-up errno.h on your system and define your own constants. You can use a script to parse errno.h and either define the constants on the fly or generate, once, the PHP code to define them.

Please be advised, however, that relying on a specific errno.h is not portable. Different systems may have different numeric values for these constants. That's why PHP should be defining the constants at compilation time and the code should be able to rely on the constant names; only the names are portable, not the actual values.
regis dot fr dot php dot net at tornad dot net
24.12.2008 16:06
A little recursive function to kill a process and his childs.
it works fine for me and I don't have find something else to do it.
It's a mix of various scripts I've found.

<?php
   
function killProcessAndChilds($pid,$signal) {
       
exec("ps -ef| awk '\$3 == '$pid' { print  \$2 }'", $output, $ret);
        if(
$ret) return 'you need ps, grep, and awk';
        while(list(,
$t) = each($output)) {
            if (
$t != $pid ) {
               
killProcessAndChilds($t,$signal);
            }
        }
       
//echo "killing ".$pid."\n";
       
posix_kill($pid, 9);
    }
?>
Jille at mydevnull dot quis dot cx
16.04.2008 15:22
If you want to test whether processes owned by other users are running, you can use:

<?php
  $running
=posix_kill($pid, 0);
  if(
posix_get_last_error()==1) /* EPERM */
   
$running=true;
?>

If the process is owned by somebody else (and you're not root), you will get an EPERM.
On my system (FreeBSD) this is defined to 1.

You should test what the value of EPERM is on your system.
Jacques Manukyan
22.03.2008 3:40
Keep in mind that you can only send kill signals to processes owned by your UID.

If you are running your program as root, then you can send kill signals to all processes.
codeslinger at compsalot dot com
2.02.2005 17:42
Detecting if another copy of a program is running (*NIX specific)

One cute trick, to see if another process is running, is to send it signal 0.  Signal 0 does not actually get sent, but kill will check to see if it is possible to send the signal.  Note that this only works if you have permission to send a signal to that process.

A practical use for this technique is to avoid running multiple copies of the same program.  You save the PID to a file in the usual way...   Then during start-up you check the value of the PID file and see if that process currently exists.

This is not totally fool-proof.  In rare circumstances it is possible for an unrelated program to have the same recycled PID.  But that other program would most likely not accept signals from your program anyway (unless your program is root). 

To make it as reliable as possible, you would want your program to remove it's PID file during shutdown (see register_shutdown_function).  That way, only if your program crashed AND another program happened to use the same PID AND the other program was willing to accept signals from your program, would you get a wrong result.  This would be an exceedingly rare occurrence.  This also assumes that the PID file has not been tampered with (as do all programs that rely on PID files...). 

It's also possible to use 'ps x' to detect this, but using kill is much more efficient.

Here is the core routine:

    $PrevPid = file_get_contents($PathToPidFile);

    if(($PrevPid !== FALSE) && posix_kill(rtrim($PrevPid),0)) {
        echo "Error: Server is already running with PID: $PrevPid\n";
        exit(-99);
    } else {
        echo "Starting Server...";
    }

Hmmm...  if you want total 100% reliability, plus efficiency.  What you could do is to make the initial check using kill.  If it says not running, then you are ready to zoom.  But if kill says already running, then you could use:

//You can get the $ProgramName from $argv[0]
$Result = shell_exec('ps x | grep "' . $PrevPid . '" | grep "' . $ProgramName . '" | grep -v "grep"');

Assuming that your program has permissions to do this.  If you execute that and get back an empty string, then the other program is an imposter using a recycled PID and you are clear to go. 

-- Erik
gid at gifpaste dot net
18.12.2002 1:26
For those that want to kill everything matching a certain pattern (ala killall in for linux), try something like this.  Note that this is a good idea to do something like this for cross platform compatilibity, instead of executing killall, because killall for other UNIXes does just that, kills EVERYTHING.  :)

function killall($match) {
    if($match=='') return 'no pattern specified';
    $match = escapeshellarg($match);
    exec("ps x|grep $match|grep -v grep|awk '{print $1}'", $output, $ret);
    if($ret) return 'you need ps, grep, and awk installed for this to work';
    while(list(,$t) = each($output)) {
        if(preg_match('/^([0-9]+)/', $t, $r)) {
            system('kill '. $r[1], $k);
            if(!$k) $killed = 1;
        }
    }
    if($killed) {
        return '';
    } else {
        return "$match: no process killed";
    }
}



PHP Powered Diese Seite bei php.net
The PHP manual text and comments are covered by the Creative Commons Attribution 3.0 License © the PHP Documentation Group - Impressum - mail("TO:Reinhard Neidl",...)