sys_sem.h(0P) POSIX Programmer's Manual sys_sem.h(0P)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.
NAME
sys/sem.h — XSI semaphore facility
SYNOPSIS
#include <sys/sem.h>
DESCRIPTION
The <sys/sem.h> header shall define the following symbolic constant for
use as a semaphore operation flag:
SEM_UNDO Set up adjust on exit entry.
The <sys/sem.h> header shall define the following symbolic constants
for use as commands for the semctl() function:
GETNCNT Get semncnt.
GETPID Get sempid.
GETVAL Get semval.
GETALL Get all cases of semval.
GETZCNT Get semzcnt.
SETVAL Set semval.
SETALL Set all cases of semval.
The <sys/sem.h> header shall define the semid_ds structure, which shall
include the following members:
struct ipc_perm sem_perm Operation permission structure.
unsigned short sem_nsems Number of semaphores in set.
time_t sem_otime Last semop() time.
time_t sem_ctime Last time changed by semctl().
The <sys/sem.h> header shall define the pid_t, size_t, and time_t types
as described in <sys/types.h>.
A semaphore shall be represented by an anonymous structure, which shall
include the following members:
unsigned short semval Semaphore value.
pid_t sempid Process ID of last operation.
unsigned short semncnt Number of processes waiting for semval
to become greater than current value.
unsigned short semzcnt Number of processes waiting for semval
to become 0.
The <sys/sem.h> header shall define the sembuf structure, which shall
include the following members:
unsigned short sem_num Semaphore number.
short sem_op Semaphore operation.
short sem_flg Operation flags.
The following shall be declared as functions and may also be defined as
macros. Function prototypes shall be provided.
int semctl(int, int, int, ...);
int semget(key_t, int, int);
int semop(int, struct sembuf *, size_t);
In addition, the <sys/sem.h> header shall include the <sys/ipc.h>
header.
The following sections are informative.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
<sys_ipc.h>, <sys_types.h>
The System Interfaces volume of POSIX.1‐2008, semctl(), semget(),
semop()COPYRIGHT
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 Electri‐
cal 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 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.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.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 sys_sem.h(0P)
