man.bsd.lv manual page server

Manual Page Search Parameters

SHMAT(2) System Calls Manual SHMAT(2)

shmat, shmdtattach or detach shared memory

library “libc”

#include <machine/param.h>
#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);

() 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:

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

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.

The XSI Interprocess Communication family of functions is also available as an implementation in userspace. To use it, the sysvipcd(8) daemon has to be running.

If the USR_SYSVIPC variable is set in a process' environment, the process and its children will use the userspace implementation.

Shmat() will fail if:

[]
No shared memory segment was found corresponding to shmid.
[]
addr was not an acceptable address.

Shmdt() will fail if:

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

shmctl(2), shmget(2)

The DragonFly specific userspace implementation (see ENVIRONMENT) was written by Larisa Grigore.

January 4, 2014 DragonFly-5.6.1