SEM_CLOSE(P)

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 .