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shmdt(2) [osf1 man page]

shmdt(2)							System Calls Manual							  shmdt(2)

NAME
shmdt - Detaches a shared memory region SYNOPSIS
#include <sys/shm.h> int shmdt( const void *addr); Application developers may want to specify #include statements for <sys/types.h> and <sys/ipc.h> before the one for <sys/shm.h> if programs are being developed for multiple platforms. The additional #include statements are not required on Tru64 UNIX systems or by ISO or X/Open standards, but may be required on other vendors' systems that conform to these stan- dards. STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: shmdt(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Specifies the starting virtual address for the shared memory region to be detached. This is the address returned by a previous shmat() call. DESCRIPTION
The shmdt() function detaches the shared memory region at the address specified by the addr parameter. Other instances of the region attached at other addresses are unaffected. RETURN VALUES
Upon successful completion, the shmdt() function decrements the value of shm_nattach in the data structure associated with the shared mem- ory ID of the attached shared memory segment and returns 0 (zero). Upon failure, the shared memory segment is not detached, -1 is returned, and errno is set to indicate the error. ERRORS
The shmdt() function sets errno to the specified values for the following conditions: The addr parameter does not specify the starting address of a shared memory region. RELATED INFORMATION
Functions: shmat(2), shmctl(2), shmget(2) Data structures: shmid_ds(4) Standards: standards(5) delim off shmdt(2)

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SHMAT(2)						      BSD System Calls Manual							  SHMAT(2)

NAME
shmat, shmdt -- map/unmap shared memory LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/shm.h> void * shmat(int shmid, const void *shmaddr, int shmflg); int shmdt(const void *shmaddr); DESCRIPTION
shmat() maps the shared memory segment associated with the shared memory identifier shmid into the address space of the calling process. The address at which the segment is mapped is determined by the shmaddr parameter. If it is equal to 0, the system will pick an address itself. Otherwise, an attempt is made to map the shared memory segment at the address shmaddr specifies. If SHM_RND is set in shmflg, the system will round the address down to a multiple of SHMLBA bytes (SHMLBA is defined in <sys/shm.h>). A shared memory segment can be mapped read-only by specifying the SHM_RDONLY flag in shmflg. shmdt() unmaps the shared memory segment that is currently mapped at shmaddr from the calling process' address space. shmaddr must be a value returned by a prior shmat() call. A shared memory segment will remain in existence until it is removed by a call to shmctl(2) with the IPC_RMID command. RETURN VALUES
shmat() returns the address at which the shared memory segment has been mapped into the calling process' address space when successful, shmdt() returns 0 on successful completion. Otherwise, a value of -1 is returned, and the global variable errno is set to indicate the error. ERRORS
shmat() will fail if: [EACCES] The calling process has no permission to access this shared memory segment. [ENOMEM] There is not enough available data space for the calling process to map the shared memory segment. [EINVAL] shmid is not a valid shared memory identifier. shmaddr specifies an illegal address. [EMFILE] The number of shared memory segments has reached the system-wide limit. shmdt() will fail if: [EINVAL] shmaddr is not the start address of a mapped shared memory segment. SEE ALSO
ipcrm(1), ipcs(1), mmap(2), shmctl(2), shmget(2) STANDARDS
The shmat and shmdt system calls conform to X/Open System Interfaces and Headers Issue 5 (``XSH5''). HISTORY
Shared memory segments appeared in the first release of AT&T System V UNIX. BSD
June 17, 2002 BSD
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