shmat (2)

Leading comments

Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>

All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   d...

(The comments found at the beginning of the groff file "man2/shmat.2freebsd".)

NAME

shmat shmdt - attach or detach shared memory

LIBRARY

Lb libc

SYNOPSIS

In sys/types.h In sys/ipc.h In sys/shm.h Ft void * Fn shmat int shmid const void *addr int flag Ft int Fn shmdt const void *addr

DESCRIPTION

The Fn shmat system call attaches the shared memory segment identified by Fa shmid to the calling process's address space. The address where the segment is attached is determined as follows:

• If Fa addr is 0, the segment is attached at an address selected by the kernel.
• If Fa addr is nonzero and SHM_RND is not specified in Fa flag , the segment is attached the specified address.
• If Fa addr is specified and SHM_RND is specified, Fa addr is rounded down to the nearest multiple of SHMLBA.

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

RETURN VALUES

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

Rv -std shmdt

ERRORS

The Fn shmat system call will fail if:

Bq Er EINVAL

No shared memory segment was found corresponding to Fa shmid .

Bq Er EINVAL

The Fa addr argument was not an acceptable address.

The Fn shmdt system call will fail if:

Bq Er EINVAL

The Fa addr argument does not point to a shared memory segment.

SEE ALSO

shmctl(2), shmget(2)