shm_attach

(PHP 4, PHP 5, PHP 7)

shm_attach ¡ª Creates or open a shared memory segment

Description

shm_attach() returns an id that can be used to access the System V shared memory with the given key, the first call creates the shared memory segment with memsize and the optional perm-bits perm.

A second call to shm_attach() for the same key will return a different shared memory identifier, but both identifiers access the same underlying shared memory. memsize and perm will be ignored.

Parameters

key

A numeric shared memory segment ID

memsize

The memory size. If not provided, default to the sysvshm.init_mem in the php.ini, otherwise 10000 bytes.

perm

The optional permission bits. Default to 0666.

Return Values

Returns a shared memory segment identifier.

Changelog

Notes

Note: This function used to return an integer value prior to PHP 5.3.0. To achieve the same value in a portable manner, the return value can be cast to an integer like: <?php //?Create?a?temporary?file?and?return?its?path $tmp?=?tempnam('/tmp',?'PHP'); //?Get?the?file?token?key $key?=?ftok($tmp,?'a'); //?Attach?the?SHM?resource,?notice?the?cast?afterwards $id?=?shm\_attach($key); if?($id?===?false)?{ ????die('Unable?to?create?the?shared?memory?segment'); } //?Cast?to?integer,?since?prior?to?PHP?5.3.0?the?resource?id? //?is?returned?which?can?be?exposed?when?casting?a?resource //?to?an?integer $id?=?(integer)?$id; ?>

See Also

• shm_detach() - Disconnects from shared memory segment

• ftok() - Convert a pathname and a project identifier to a System V IPC key

¡û sem_remove

shm_detach ¡ú

Licensed under the Creative Commons Attribution License v3.0 or later.

https://secure.php.net/manual/en/function.shm-attach.php