shmop_open(3) [php man page]

SHMOP_OPEN(3)								 1							     SHMOP_OPEN(3)

shmop_open - Create or open shared memory block

SYNOPSIS

       int shmop_open (int  $key, string  $flags, int  $mode, int  $size)

DESCRIPTION

       shmop_open(3) can create or open a shared memory block.

PARAMETERS

	      o $key
		- System's id for the shared memory block. Can be passed as a decimal or hex.

	      o $flags
		- The flags that you can use:

		     o	"a"  for access (sets SHM_RDONLY for shmat) use this flag when you need to open an existing shared memory segment for read
		     only

		     o "c" for create (sets IPC_CREATE) use this flag when you need to create a new shared memory segment or if a segment with the
		     same key exists, try to open it for read and write

		     o "w" for read & write access use this flag when you need to read and write to a shared memory segment, use this flag in most
		     cases.

		     o "n" create a new memory segment (sets IPC_CREATE|IPC_EXCL) use this flag when you want to create a new shared  memory  seg-
		     ment  but	if  one  already exists with the same flag, fail. This is useful for security purposes, using this you can prevent
		     race condition exploits.

	      o $mode
		- The permissions that you wish to assign to your memory segment, those are the same as permission for a file. Permissions need to
		be passed in octal form, like for example 0644

	      o $size
		- The size of the shared memory block you wish to create in bytes

       Note

	       Note: the 3rd and 4th should be entered as 0 if you are opening an existing memory segment.

RETURN VALUES

	On  success  shmop_open(3)  will  return  an id that you can use to access the shared memory segment you've created.  FALSE is returned on
       failure.

EXAMPLES

       Example #1

	      Create a new shared memory block

	      <?php
	      $shm_key = ftok(__FILE__, 't');
	      $shm_id = shmop_open($shm_key, "c", 0644, 100);
	      ?>

	This example opened a shared memory block with a system id returned by ftok(3).

SEE ALSO

       shmop_close(3), shmop_delete(3).

PHP Documentation Group 													     SHMOP_OPEN(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