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
semaphore 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 successfully invoked for name after the
most recent call to sem_open() with O_CREAT for this semaphore, then
when all processes 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, Copyright (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.opengroup.org/unix/online.html .