sys_shm.h(7POSIX) POSIX Programmer's Manual sys_shm.h(7POSIX)
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.
sys/shm.h — XSI shared memory facility
The <sys/shm.h> header shall define the following symbolic constants:
SHM_RDONLY Attach read-only (else read-write).
SHM_RND Round attach address to SHMLBA.
SHMLBA Segment low boundary address multiple.
The <sys/shm.h> header shall define the following data types through typedef:
shmatt_t Unsigned integer used for the number of current attaches that must be able to
store values at least as large as a type unsigned short.
The <sys/shm.h> header shall define the shmid_ds structure, which shall include the fol‐
struct ipc_perm shm_perm Operation permission structure.
size_t shm_segsz Size of segment in bytes.
pid_t shm_lpid Process ID of last shared memory operation.
pid_t shm_cpid Process ID of creator.
shmatt_t shm_nattch Number of current attaches.
time_t shm_atime Time of last shmat().
time_t shm_dtime Time of last shmdt().
time_t shm_ctime Time of last change by shmctl().
The <sys/shm.h> header shall define the pid_t, size_t, and time_t types as described in
The following shall be declared as functions and may also be defined as macros. Function
prototypes shall be provided.
void *shmat(int, const void *, int);
int shmctl(int, int, struct shmid_ds *);
int shmdt(const void *);
int shmget(key_t, size_t, int);
In addition, the <sys/shm.h> header shall include the <sys/ipc.h> header.
The following sections are informative.
The System Interfaces volume of POSIX.1‐2008, shmat(), shmctl(), shmdt(), shmget()
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrep‐
ancy 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.unix.org/online.html .
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 .
IEEE/The Open Group 2013 sys_shm.h(7POSIX)