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.TH SHMOP 2
.SH NAME
shmop \- shared memory operations
.SH SYNOPSIS
.B #include <sys/types.h>
.br
.B #include <sys/ipc.h>
.br
.B #include <sys/shm.h>
.PP
.nf
.B char \(**shmat (shmid, shmaddr, shmflg)
.B int shmid;
.B char \(**shmaddr
.B int shmflg;
.PP
.B int shmdt (shmaddr)
.B char \(**shmaddr
.fi
.SH DESCRIPTION
.I Shmat
attaches the shared memory segment associated with the shared memory identifier
specified by
.I shmid
to the data segment of the calling process.
The segment is attached at the address specified by one of the following
criteria:
.IP
If
.I shmaddr
is equal to zero, the segment is attached at the first available address as
selected by the system.
.IP
If
.I shmaddr
is not equal to zero and
.RI ( shmflg " &"
.SM
.B SHM_RND\*S)
is ``true'', the segment is attached at the address given by
.RI ( shmaddr " -" 
.RI ( shmaddr " modulus"
.SM
.BR SHMLBA\*S "))."
.IP
If
.I shmaddr
is not equal to zero and
.RI ( shmflg " &"
.SM
.B SHM_RND\*S)
is ``false'', the segment is attached at the address given by
.IR shmaddr .
.PP
The segment is attached for reading if
.RI ( shmflg " &"
.SM
.B SHM_RDONLY\*S)
is ``true''
.SM
\%{READ}\*S,
otherwise it is attached for reading and writing
.SM
\%{READ/WRITE}\*S.
.PP
.I Shmat
fails and not attach the shared memory segment if one or more of the
following is true:
.TP 15
.SM
\%[EINVAL]
.I Shmid
is not a valid shared memory identifier.
.TP
.SM
\% [EACCES]
Operation permission is denied to the calling process (see
.IR intro (2)).
.TP
.SM
\%[ENOMEM]
The available data space 
is not large enough to accommodate the shared memory segment.
.TP
.SM
\%[EINVAL]
.I Shmaddr
is not equal to zero, and the value of
.RI ( shmaddr " -" 
.RI ( shmaddr " modulus"
.SM
.BR SHMLBA\*S "))"
is an illegal address.
.TP
.SM
\%[EINVAL]
.I Shmaddr
is not equal to zero,
.RI ( shmflg " &"
.SM
.B SHM_RND\*S)
is ``false'', and the value of
.I shmaddr
is an illegal address.
.TP
.SM
\%[EMFILE]
The number of shared memory segments attached to the calling process would
exceed the system-imposed limit.
.PP
.TP 15
.SM
\%[EINVAL]
.I Shmdt
detaches from the calling process's data segment
the shared memory segment located at the address specified by
.IR shmaddr.
.PP
.TP 15
.SM
\%[EINVAL]
.I Shmdt
fails and not detach the shared memory segment if
.I shmaddr
is not the data segment start address of a shared memory segment.
.SH RETURN VALUES
Upon successful completion, the return value is as follows:
.br
.ne 8v
.IP
.I Shmat
returns the data segment start address of the attached shared memory segment.
.IP
.I Shmdt
returns a value of 0.
.PP
Otherwise, a value of \-1 is returned and
.I errno
is set to indicate the error.
.SH SEE ALSO
exec(2), exit(2), fork(2), intro(2), shmctl(2), shmget(2).
.\"	@(#)shmop.2	6.2 of 9/6/83

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