sem_get

Description

resource sem_get ( int key [, int max_acquire [, int perm [, int auto_release]]] )

sem_get() returns an id that can be used to access the System V semaphore with the given key. The semaphore is created if necessary using the permission bits specified in perm (defaults to 0666). The number of processes that can acquire the semaphore simultaneously is set to max_acquire (defaults to 1). Actually this value is set only if the process finds it is the only process currently attached to the semaphore.

Optional parameter auto_release specifies if the semaphore should be automatically released on request shutdown. It is available since PHP 4.3.0.

Returns a positive semaphore identifier on success, or FALSE on error.

A second call to sem_get() for the same key will return a different semaphore identifier, but both identifiers access the same underlying semaphore.

add a note User Contributed Notes

neofutur
29-Aug-2006 03:49


with gentoo php5 you will need to add the USE flag :

sysvipc



see :

 http://forums.gentoo.org/viewtopic-t-464175-highlight-semget+php.html



and also :

 http://overlays.gentoo.org/proj/php/

joeldg AT listbid.com
03-May-2003 02:39


Heh, actually the above comment I added is not technically correct, it was more of an idea to display the function.



$SHM_KEY = ftok("/home/joeldg/homeymail/shmtest.php", 'R');

$shmid = sem_get($SHM_KEY, 1024, 0644 | IPC_CREAT);

$data = shm_attach($shmid, 1024);

// we now have our shm segment



// lets place a variable in there

shm_put_var ($data, $inmem, "test");

// now lets get it back. we could be in a forked process and still have

// access to this variable.

printf("shared contents: %s\n", shm_get_var($data, $inmem));



shm_detach($data);

joeldg at listbid.com
02-May-2003 03:36


<?

// thanks to

// http://www.ecst.csuchico.edu/~beej/guide/ipc/shmem.html

$SHM_KEY = ftok("/home/joeldg/homeymail/shmtest.php", 'R');

$shmid = sem_get($SHM_KEY, 1024, 0644 | IPC_CREAT);

$data = shm_attach($shmid, 1024);



$data = "test";

printf("shared contents: %s\n", $data);



shm_detach($data);

?>

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