NAME
sem_unlink —
remove a named semaphore
SYNOPSIS
#include
<semaphore.h>
int sem_unlink(const char *name);
DESCRIPTION
The sem_unlink () function shall remove
the semaphore named by the string name. If the semaphore
named by name is currently referenced by other processes,
then sem_unlink () shall have no effect on the state
of the semaphore. If one or more processes have the semaphore open when
sem_unlink () is called, destruction of the
semaphore is postponed until all references to the semaphore have been
destroyed by calls to sem_close(3),
_exit(3), or
exec.
Calls to sem_open(3) to recreate or reconnect to the
semaphore refer to a new semaphore after sem_unlink
() is called. The sem_unlink () call shall not block
until all references have been destroyed; it shall return immediately.
RETURN VALUE
Upon successful completion, the sem_unlink
() function shall return a value of 0. Otherwise, the semaphore shall not be
changed and the function shall return a value of -1 and set
errno to
indicate the error.
ERRORS
The sem_unlink () function shall fail
if:
- [EACCES]
- Permission is denied to unlink the named semaphore.
- [ENOENT]
- The named semaphore does not exist.
The sem_unlink () function may fail
if:
- [ENAMETOOLONG]
- The length of the name argument exceeds {_POSIX_PATH_MAX} on systems that
do not support the XSI option [XSI] or exceeds {_XOPEN_PATH_MAX} on XSI
systems, or has a pathname component that is longer than {_POSIX_NAME_MAX}
on systems that do not support the XSI option [XSI] or longer than
{_XOPEN_NAME_MAX} on XSI systems. A call to
sem_unlink() with a name argument that contains the same semaphore name as was previously used in a successful sem_open () call shall not give an [ENAMETOOLONG] error.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
A future version might require the sem_open(3)
and sem_unlink () functions to have semantics
similar to normal file system operations.
SEE ALSO
semctl(3), semget(3), semop(3), sem_close(3), sem_open(3)
XBD <semaphore.h>
CHANGE HISTORY
First released in Issue 5. Included for alignment with the POSIX Realtime Extension.
Issue 6
The sem_unlink () function is marked as
part of the Semaphores option.
The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Semaphores option.
Issue 7
Austin Group Interpretation 1003.1-2001 #077 is applied, changing [ENAMETOOLONG] from a ``shall fail'' to a ``may fail'' error.
Austin Group Interpretation 1003.1-2001 #141 is applied, adding FUTURE DIRECTIONS.
The sem_unlink () function is moved from
the Semaphores option to the Base.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0531 [37] is applied.