PROLOG | NAME | SYNOPSIS | DESCRIPTION | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

sys_sem.h(0P)             POSIX Programmer's Manual            sys_sem.h(0P)

PROLOG         top

       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         top

       sys/sem.h — XSI semaphore facility

SYNOPSIS         top

       #include <sys/sem.h>

DESCRIPTION         top

       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         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       sys_ipc.h(0p), sys_types.h(0p)

       The System Interfaces volume of POSIX.1‐2008, semctl(3p), semget(3p),
       semop(3p)

COPYRIGHT         top

       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 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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                       sys_sem.h(0P)

Pages that refer to this page: semctl(3p)semget(3p)semop(3p)