SEM_CLOSE(3P)                                       POSIX Programmer's Manual                                      SEM_CLOSE(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       sem_close - close a named semaphore (REALTIME)

SYNOPSIS
       #include <semaphore.h>

       int sem_close(sem_t *sem);


DESCRIPTION
       The  sem_close() function shall indicate that the calling process is finished using the named semaphore indicated by sem.
       The effects of calling sem_close() for an unnamed semaphore (one created by sem_init()) are  undefined.  The  sem_close()
       function  shall  deallocate  (that  is,  make  available for reuse by a subsequent sem_open() by this process) any system
       resources allocated by the system for use by this process for this semaphore. The effect of subsequent use of  the  sema-
       phore  indicated  by  sem  by  this process is undefined. If the semaphore has not been removed with a successful call to
       sem_unlink(), then sem_close() has no effect on the state of the semaphore.  If the sem_unlink() function has  been  suc-
       cessfully  invoked  for name after the most recent call to sem_open() with O_CREAT for this semaphore, then when all pro-
       cesses that have opened the semaphore close it, the semaphore is no longer accessible.

RETURN VALUE
       Upon successful completion, a value of zero shall be returned. Otherwise, a value of -1 shall be returned and  errno  set
       to indicate the error.

ERRORS
       The sem_close() function shall fail if:

       EINVAL The sem argument is not a valid semaphore descriptor.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The sem_close() function is part of the Semaphores option and need not be available on all implementations.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       semctl(),  semget(),  semop(), sem_init(), sem_open(), sem_unlink(), the Base Definitions volume of IEEE Std 1003.1-2001,
       <semaphore.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                 SEM_CLOSE(3P)