| SEM_INIT(3) | Library Functions Manual | SEM_INIT(3) |
sem_init —
initialize an unnamed semaphore
#include
<semaphore.h>
int
sem_init(sem_t
*sem, int pshared,
unsigned int value);
The
sem_init()
function initializes the unnamed semaphore pointed to by
sem to have the value value. A
non-zero value for pshared specifies a shared
semaphore that can be used by multiple processes, which this implementation
is not capable of.
Following a successful call to
sem_init(),
sem can be used as an argument in subsequent calls to
sem_wait, sem_trywait,
sem_post, and sem_destroy.
sem is no longer valid after a successful call to
sem_destroy.
The sem_init() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno is set to indicate the
error.
It is an error to call sem_destroy() on a
named semaphore created by sem_open().
sem_init() will fail if:
sem_destroy(3), sem_getvalue(3), sem_open(3), sem_post(3), sem_wait(3)
sem_init() conforms to
ISO/IEC 9945-1:1996 (“POSIX.1”).
This implementation does not support shared semaphores, and
reports this fact by setting errno to
EPERM. This is perhaps a stretch of the intention of
POSIX, but is compliant, with the caveat that
sem_init() always reports a permissions error when
an attempt to create a shared semaphore is made.
| April 6, 2021 | OpenBSD-current |