shm_attach(3) [php man page]
SHM_ATTACH(3) 1 SHM_ATTACH(3) shm_attach - Creates or open a shared memory segment SYNOPSIS
resource shm_attach (int $key, [int $memsize], [int $perm = 0666]) DESCRIPTION
shm_attach(3) 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(3) 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
o $key - A numeric shared memory segment ID o $memsize - The memory size. If not provided, default to the sysvshm.init_mem in the php.ini, otherwise 10000 bytes. o $perm - The optional permission bits. Default to 0666. RETURN VALUES
Returns a shared memory segment identifier. CHANGELOG
+--------+---------------------------------------------------+ |Version | | | | | | | Description | | | | +--------+---------------------------------------------------+ | 5.3.0 | | | | | | | This function now returns a resource instead of | | | an integer. | | | | +--------+---------------------------------------------------+ 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: Example #1 <?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(3), ftok(3). PHP Documentation Group SHM_ATTACH(3)
Check Out this Related Man Page
shmget(2) System Calls shmget(2) NAME
shmget - get shared memory segment identifier SYNOPSIS
#include <sys/types.h> #include <sys/ipc.h> #include <sys/shm.h> int shmget(key_t key, size_t size, int shmflg); DESCRIPTION
The shmget() function returns the shared memory identifier associated with key. A shared memory identifier and associated data structure and shared memory segment of at least size bytes (see Intro(2)) are created for key if one of the following are true: o The key argument is equal to IPC_PRIVATE. o The key argument does not already have a shared memory identifier associated with it, and (shmflg&IPC_CREAT) is true. Upon creation, the data structure associated with the new shared memory identifier is initialized as follows: o The values of shm_perm.cuid, shm_perm.uid, shm_perm.cgid, and shm_perm.gid are set equal to the effective user ID and effective group ID, respectively, of the calling process. o The access permission bits of shm_perm.mode are set equal to the access permission bits of shmflg. shm_segsz is set equal to the value of size. o The values of shm_lpid, shm_nattch shm_atime, and shm_dtime are set equal to 0. o The shm_ctime is set equal to the current time. Shared memory segments must be explicitly removed after the last reference to them has been removed. RETURN VALUES
Upon successful completion, a non-negative integer representing a shared memory identifier is returned. Otherwise, -1 is returned and errno is set to indicate the error. ERRORS
The shmget() function will fail if: EACCES A shared memory identifier exists for key but operation permission (see Intro(2)) as specified by the low-order 9 bits of shmflg would not be granted. EEXIST A shared memory identifier exists for key but both (shmflg&IPC_CREAT) and (shmflg&IPC_EXCL) are true. EINVAL The size argument is less than the system-imposed minimum or greater than the system-imposed maximum. See NOTES. A shared memory identifier exists for key but the size of the segment associated with it is less than size and size is not equal to 0. ENOENT A shared memory identifier does not exist for key and (shmflg&IPC_CREAT) is false. ENOMEM A shared memory identifier and associated shared memory segment are to be created but the amount of available memory is not suf- ficient to fill the request. ENOSPC A shared memory identifier is to be created but the system-imposed limit on the maximum number of allowed shared memory identi- fiers system-wide would be exceeded. See NOTES. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
rctladm(1M), Intro(2), setrctl(2), shmctl(2), shmop(2), ftok(3C), getpagesize(3C), attributes(5), standards(5) NOTES
The project.max-shm-memory resource control restricts the total amount of shared memory a project can allocate. The zone.max-shm-memory resource control restricts the total amount of shared memory that can be allocated by a zone. The system-imposed maximum on the size of a shared memory segment is therefore a function of the sizes of any other shared memory segments the calling project might have allocated that are still in use, as well as any other shared memory segments allocated and still in use by processes in the zone. For accounting purposes, segment sizes are rounded up to the nearest multiple of the system page size. See getpagesize(3C). The system-imposed limit on the number of shared memory identifiers is maintained on a per-project basis using the project.max-shm-ids resource control. The zone.max-shm-ids resource control restricts the total number of shared memory identifiers that can be allocated by a zone. See rctladm(1M) and setrctl(2) for information about using resource controls. SunOS 5.11 14 Aug 2006 shmget(2)