The sem_close() function is used to 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(3RT)) are undefined. The sem_close() function deallocates (that is, make available for reuse by a subsequent sem_open(3RT) 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(3RT), then sem_close() has no effect on the state of the semaphore. If the sem_unlink(3RT) function has been successfully invoked for name after the most recent call to sem_open(3RT) with O_CREAT for this semaphore, then when all processes that have opened the semaphore close it, the semaphore is no longer be accessible.

If successful, sem_close() returns 0, otherwise it returns -1 and sets errno to indicate the error.

The sem_close() function will fail if:

EINVAL

The sem argument is not a valid semaphore descriptor.

ENOSYS

The sem_close() function is not supported by the system.

The sem_close() function should not be called for an unnamed semaphore initialized by sem_init(3RT).

See attributes(5) for descriptions of the following attributes:

sem_init(3RT), sem_open(3RT), sem_unlink(3RT), attributes(5)

Solaris 2.6 was the first release to support the Asynchronous Input and Output option. Prior to this release, this function always returned -1 and set errno to ENOSYS.