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124 lines
4.2 KiB
Plaintext
124 lines
4.2 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "SHMAT" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" shmat
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.SH NAME
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shmat \- XSI shared memory attach operation
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.SH SYNOPSIS
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.LP
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\fB#include <sys/shm.h>
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.br
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.sp
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void *shmat(int\fP \fIshmid\fP\fB, const void *\fP\fIshmaddr\fP\fB,
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int\fP \fIshmflg\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIshmat\fP() function operates on XSI shared memory (see the
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Base Definitions volume of IEEE\ Std\ 1003.1-2001, Section 3.340,
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Shared Memory Object). It is unspecified whether this function
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interoperates with the realtime interprocess communication facilities
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defined in \fIRealtime\fP .
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.LP
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The \fIshmat\fP() function attaches the shared memory segment associated
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with the shared memory identifier specified by
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\fIshmid\fP to the address space of the calling process. The segment
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is attached at the address specified by one of the following
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criteria:
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.IP " *" 3
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If \fIshmaddr\fP is a null pointer, the segment is attached at the
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first available address as selected by the system.
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.LP
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.IP " *" 3
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If \fIshmaddr\fP is not a null pointer and (\fIshmflg\fP &SHM_RND)
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is non-zero, the segment is attached at the address
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given by (\fIshmaddr\fP -((\fIuintptr_t\fP)\fIshmaddr\fP %SHMLBA)).
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The character \fB'%'\fP is the C-language remainder
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operator.
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.LP
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.IP " *" 3
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If \fIshmaddr\fP is not a null pointer and (\fIshmflg\fP &SHM_RND)
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is 0, the segment is attached at the address given by
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\fIshmaddr\fP.
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.LP
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.IP " *" 3
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The segment is attached for reading if (\fIshmflg\fP &SHM_RDONLY)
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is non-zero and the calling process has read permission;
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otherwise, if it is 0 and the calling process has read and write permission,
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the segment is attached for reading and writing.
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.LP
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.SH RETURN VALUE
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.LP
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Upon successful completion, \fIshmat\fP() shall increment the value
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of \fIshm_nattch\fP in the data structure associated with
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the shared memory ID of the attached shared memory segment and return
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the segment's start address.
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.LP
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Otherwise, the shared memory segment shall not be attached, \fIshmat\fP()
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shall return -1, and \fIerrno\fP shall be set to
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indicate the error.
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.SH ERRORS
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.LP
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The \fIshmat\fP() function shall fail if:
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.TP 7
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.B EACCES
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Operation permission is denied to the calling process; see \fIXSI
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Interprocess
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Communication\fP .
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.TP 7
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.B EINVAL
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The value of \fIshmid\fP is not a valid shared memory identifier,
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the \fIshmaddr\fP is not a null pointer, and the value of
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(\fIshmaddr\fP -((\fIuintptr_t\fP)\fIshmaddr\fP %SHMLBA)) is an illegal
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address for attaching shared memory; or the
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\fIshmaddr\fP is not a null pointer, (\fIshmflg\fP &SHM_RND) is 0,
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and the value of \fIshmaddr\fP is an illegal address for
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attaching shared memory.
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.TP 7
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.B EMFILE
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The number of shared memory segments attached to the calling process
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would exceed the system-imposed limit.
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.TP 7
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.B ENOMEM
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The available data space is not large enough to accommodate the shared
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memory segment.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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The POSIX Realtime Extension defines alternative interfaces for interprocess
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communication. Application developers who need to
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use IPC should design their applications so that modules using the
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IPC routines described in \fIXSI Interprocess Communication\fP can
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be easily modified to use the alternative
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interfaces.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIXSI Interprocess Communication\fP , \fIRealtime\fP , \fIexec\fP()
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,
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\fIexit\fP() , \fIfork\fP() , \fIshmctl\fP() , \fIshmdt\fP() , \fIshmget\fP()
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, \fIshm_open\fP() ,
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\fIshm_unlink\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
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\fI<sys/shm.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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