SHMOP(2) DOMAIN/IX Reference Manual (SYS5) SHMOP(2)
NAME
shmop - shared memory operations
USAGE
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
char *shmat (shmid, shmaddr, shmflg)
int shmid;
char *shmaddr
int shmflg;
int shmdt (shmaddr)
char *shmaddr
DESCRIPTION
Shmat attaches the shared memory segment associated with the
shared memory identifier shmid to the data segment of the
calling process. The segment is attached at the address
specified by one of the following criteria:
If shmaddr is equal to zero, the segment is attached at
the first available address the system selects.
If shmaddr is not equal to zero and (shmflg & SHM_RND)
is ``true'', the segment is attached at the address
given by (shmaddr - (shmaddr modulus SHMLBA)).
If shmaddr is not equal to zero and (shmflg & SHM_RND)
is ``false'', the segment is attached at the address
given by shmaddr.
The segment is attached for reading if (shmflg & SHM_RDONLY)
is ``true'' {READ}; otherwise, it is attached for reading
and writing {READ/WRITE}.
RETURN VALUES
Upon successful completion, the return value is as follows:
Shmat returns the data segment start address of the
attached shared memory segment.
Shmdt returns a value of zero.
Otherwise, a value of -1 is returned and errno is set to
indicate the error.
ERRORS
Shmat will fail and not attach the shared memory segment if
one or more of the following is true:
Printed 5/10/85 SHMOP-1
SHMOP(2) DOMAIN/IX Reference Manual (SYS5) SHMOP(2)
[EINVAL] Shmid is not a valid shared memory identif-
ier.
[EACCES] Operation permission is denied to the calling
process (see intro(2)).
[ENOMEM] The available data space is not large enough
to accommodate the shared memory segment.
[EINVAL] Shmaddr is not equal to zero, and the value
of (shmaddr - (shmaddr modulus SHMLBA)) is an
illegal address.
[EINVAL] Shmaddr is not equal to zero, (shmflg &
SHM_RND) is ``false'', and the value of
shmaddr is an illegal address.
[EMFILE] The number of shared memory segments attached
to the calling process would exceed the
system-imposed limit.
[EINVAL] Shmdt detaches from the calling process' data
segment the shared memory segment located at
the address specified by shmaddr.
[EINVAL] Shmdt will fail and not detach the shared
memory segment if shmaddr is not the data
segment start address of a shared memory seg-
ment.
RELATED INFORMATION
exec(2), exit(2), fork(2), shmctl(2), shmget(2)
SHMOP-2 Printed 5/10/85