xenial (7) sys_sem.h.7posix.gz

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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()


       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 .