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)

SHMGET(2)						      BSD System Calls Manual							 SHMGET(2)

NAME

     shmget -- get shared memory area identifier

SYNOPSIS

     #include <sys/shm.h>

     int
     shmget(key_t key, size_t size, int shmflg);

DESCRIPTION

     shmget() returns the shared memory identifier associated with the key key.

     A shared memory segment is created if either key is equal to IPC_PRIVATE, or key does not have a shared memory segment identifier associated
     with it, and the IPC_CREAT bit is set in shmflg.

     If a new shared memory segment is created, the data structure associated with it (the shmid_ds structure, see shmctl(2)) is initialized as
     follows:

     o	 shm_perm.cuid and shm_perm.uid are set to the effective uid of the calling process.

     o	 shm_perm.gid and shm_perm.cgid are set to the effective gid of the calling process.

     o	 shm_perm.mode is set to the lower 9 bits of shmflg.

     o	 shm_lpid, shm_nattch, shm_atime, and shm_dtime are set to 0

     o	 shm_ctime is set to the current time.

     o	 shm_segsz is set to the value of size.

     o	 The ftok(3) function may be used to generate a key from a pathname.

RETURN VALUES

     Upon successful completion a positive shared memory segment identifier is returned.  Otherwise, -1 is returned and the global variable errno
     is set to indicate the error.

ERRORS

     The shmget() system call will fail if:

     [EACCES]		A shared memory segment is already associated with key and the caller has no permission to access it.

     [EEXIST]		Both IPC_CREAT and IPC_EXCL are set in shmflg, and a shared memory segment is already associated with key.

     [EINVAL]		No shared memory segment is to be created, and a shared memory segment exists for key, but the size of the segment associ-
			ated with it is less than size, which is non-zero.

     [ENOENT]		IPC_CREAT was not set in shmflg and no shared memory segment associated with key was found.

     [ENOMEM]		There is not enough memory left to created a shared memory segment of the requested size.

     [ENOSPC]		A new shared memory identifier could not be created because the system limit for the number of shared memory identifiers
			has been reached.

LEGACY SYNOPSIS

     #include <sys/types.h>
     #include <sys/ipc.h>
     #include <sys/shm.h>

     int
     shmget(key_t key, int size, int shmflg);

     All of these include files are necessary.	The type of size has changed.

SEE ALSO

     ftok(3), shmat(2), shmctl(2), shmdt(2), compat(5)

BSD
								  August 17, 1995							       BSD