The shm_open() function shall establish a connection between a shared memory object and a file descriptor. It shall create an open file description that refers to the shared memory object and a file descriptor that refers to that open file description. The file descriptor shall be allocated as described in 2.6 File Descriptor Allocation, and can be used by other functions to refer to that shared memory object. The name argument points to a string naming a shared memory object. It is unspecified whether the name appears in the file system and is visible to other functions that take pathnames as arguments. The name argument conforms to the construction rules for a pathname, except that the interpretation of <slash> characters other than the leading <slash> character in name is implementation-defined, and that the length limits for the name argument are implementation-defined and need not be the same as the pathname limits {PATH_MAX} and {NAME_MAX}. If name begins with the <slash> character, then processes calling shm_open() with the same value of name refer to the same shared memory object, as long as that name has not been removed. If name does not begin with the <slash> character, the effect is implementation-defined.

The shm_open() function shall establish a connection between a shared memory object and a file descriptor. It shall create an open file description that refers to the shared memory object and a file descriptor that refers to that open file description. The file descriptor shall be allocated as described in 2.6 File Descriptor Allocation, and can be used by other functions to refer to that shared memory object. The name argument points to a string naming a shared memory object or SHM_ANON constant. It is unspecified whether the name appears in the file system and is visible to other functions that take pathnames as arguments. The name argument conforms to the construction rules for a pathname, except that the interpretation of <slash> characters other than the leading <slash> character in name is implementation-defined, and that the length limits for the name argument are implementation-defined and need not be the same as the pathname limits {PATH_MAX} and {NAME_MAX}. If name begins with the <slash> character, then processes calling shm_open() with the same value of name refer to the same shared memory object, as long as that name has not been removed. If name does not begin with the <slash> character, the effect is implementation-defined. if name is SHM_ANON, then an unnamed shared memory object shall be created. Since the shared memory object has no associated name, it cannot be removed with shm_unlink() and instead it will be destroyed once last reference to it is removed.