'\" et
.TH sys_shm.h "0P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
sys/shm.h
\(em XSI shared memory facility
.SH SYNOPSIS
.LP
.nf
#include <sys/shm.h>
.fi
.SH DESCRIPTION
The
.IR <sys/shm.h> 
header shall define the following symbolic constants:
.IP SHM_RDONLY 12
Attach read-only (else read-write).
.IP SHM_RND 12
Round attach address to SHMLBA.
.IP SHMLBA 12
Segment low boundary address multiple.
.P
The
.IR <sys/shm.h> 
header shall define the following data types through
.BR typedef :
.IP "\fBshmatt_t\fP" 12
Unsigned integer used for the number of current attaches that must be
able to store values at least as large as a type
.BR "unsigned short" .
.P
The
.IR <sys/shm.h> 
header shall define the
.BR shmid_ds
structure, which shall include the following members:
.sp
.RS 4
.nf

struct ipc_perm shm_perm   \fROperation permission structure.\fR
size_t          shm_segsz  \fRSize of segment in bytes.\fR
pid_t           shm_lpid   \fRProcess ID of last shared memory operation.\fR
pid_t           shm_cpid   \fRProcess ID of creator.\fR
shmatt_t        shm_nattch \fRNumber of current attaches.\fR
time_t          shm_atime  \fRTime of last \fIshmat\fP\^(\|).\fR
time_t          shm_dtime  \fRTime of last \fIshmdt\fP\^(\|).\fR
time_t          shm_ctime  \fRTime of last change by \fIshmctl\fP\^(\|).\fR
.fi
.P
.RE
.P
The
.IR <sys/shm.h> 
header shall define the
.BR pid_t ,
.BR size_t ,
and
.BR time_t
types as described in
.IR <sys/types.h> .
.P
The following shall be declared as functions and may also be defined
as macros. Function prototypes shall be provided.
.sp
.RS 4
.nf

void *shmat(int, const void *, int);
int   shmctl(int, int, struct shmid_ds *);
int   shmdt(const void *);
int   shmget(key_t, size_t, int);
.fi
.P
.RE
.P
In addition, the
.IR <sys/shm.h> 
header shall include the
.IR <sys/ipc.h> 
header.
.LP
.IR "The following sections are informative."
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fB<sys_ipc.h>\fP",
.IR "\fB<sys_types.h>\fP"
.P
The System Interfaces volume of POSIX.1\(hy2017,
.IR "\fIshmat\fR\^(\|)",
.IR "\fIshmctl\fR\^(\|)",
.IR "\fIshmdt\fR\^(\|)",
.IR "\fIshmget\fR\^(\|)"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .