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SHMAT(2)		  FreeBSD System Calls Manual		      SHMAT(2)

NAME
     shmat, shmdt -- attach or detach shared memory

LIBRARY
     Standard C	Library	(libc, -lc)

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

     void *
     shmat(int shmid, const void *addr,	int flag);

     int
     shmdt(const void *addr);

DESCRIPTION
     The shmat() system	call attaches the shared memory	segment	identified by
     shmid to the calling process's address space.  The	address	where the seg-
     ment is attached is determined as follows:

     +o	 If addr is 0, the segment is attached at an address selected by the
	 kernel.

     +o	 If addr is nonzero and	SHM_RND	is not specified in flag, the segment
	 is attached the specified address.

     +o	 If addr is specified and SHM_RND is specified,	addr is	rounded	down
	 to the	nearest	multiple of SHMLBA.

     The shmdt() system	call detaches the shared memory	segment	at the address
     specified by addr from the	calling	process's address space.

RETURN VALUES
     Upon success, shmat() returns the address where the segment is attached;
     otherwise,	-1 is returned and errno is set	to indicate the	error.

     The shmdt() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     The shmat() system	call will fail if:

     [EINVAL]		No shared memory segment was found corresponding to
			shmid.

     [EINVAL]		The addr argument was not an acceptable	address.

     The shmdt() system	call will fail if:

     [EINVAL]		The addr argument does not point to a shared memory
			segment.

SEE ALSO
     shmctl(2),	shmget(2)

FreeBSD	10.1			August 2, 1995			  FreeBSD 10.1

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO

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