sys_sem.h(3)               POSIX Programmer's Manual              sys_sem.h(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NNAAMMEE
       sys/sem.h -- XSI semaphore facility

SSYYNNOOPPSSIISS
       #include <sys/sem.h>

DDEESSCCRRIIPPTTIIOONN
       The _<_s_y_s_/_s_e_m_._h_> header shall define the following symbolic constant for
       use as a semaphore operation flag:

       SEM_UNDO    Set up adjust on exit entry.

       The _<_s_y_s_/_s_e_m_._h_> header shall define the following symbolic constants
       for use as commands for the _s_e_m_c_t_l() function:

       GETNCNT     Get _s_e_m_n_c_n_t.

       GETPID      Get _s_e_m_p_i_d.

       GETVAL      Get _s_e_m_v_a_l.

       GETALL      Get all cases of _s_e_m_v_a_l.

       GETZCNT     Get _s_e_m_z_c_n_t.

       SETVAL      Set _s_e_m_v_a_l.

       SETALL      Set all cases of _s_e_m_v_a_l.

       The _<_s_y_s_/_s_e_m_._h_> header shall define the sseemmiidd__ddss 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 _s_e_m_o_p() time.
           time_t           sem_ctime Last time changed by _s_e_m_c_t_l().

       The _<_s_y_s_/_s_e_m_._h_> header shall define the ppiidd__tt, ssiizzee__tt, and ttiimmee__tt types
       as described in _<_s_y_s_/_t_y_p_e_s_._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 _s_e_m_v_a_l
                                    to become greater than current value.
           unsigned short  semzcnt  Number of processes waiting for _s_e_m_v_a_l
                                    to become 0.

       The _<_s_y_s_/_s_e_m_._h_> header shall define the sseemmbbuuff 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 _<_s_y_s_/_s_e_m_._h_> header shall include the _<_s_y_s_/_i_p_c_._h_>
       header.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       <<ssyyss__iippcc..hh>>, <<ssyyss__ttyyppeess..hh>>

       The System Interfaces volume of POSIX.1-2017, _s_e_m_c_t_l(), _s_e_m_g_e_t(),
       _s_e_m_o_p()

CCOOPPYYRRIIGGHHTT
       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 .

       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                  2017                         sys_sem.h(3)
