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SHMAT(2) | 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¶
Theshmat
() system call attaches the shared
memory segment identified by shmid to the
calling process's address space. The address where the segment is attached is
determined as follows:
- If addr is 0, the segment is attached at an address selected by the kernel.
- If addr is nonzero and SHM_RND is not specified in flag, the segment is attached the specified address.
- If addr is specified and SHM_RND is specified, addr is rounded down to the nearest multiple of SHMLBA.
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¶
Theshmat
() system call will fail if:
- [
EINVAL
] - No shared memory segment was found corresponding to shmid.
- [
EINVAL
] - The addr argument was not an acceptable address.
shmdt
() system call will fail if:
- [
EINVAL
] - The addr argument does not point to a shared memory segment.
SEE ALSO¶
shmctl(2), shmget(2)August 2, 1995 | Debian |