| SEM_WAIT(3) | Library Functions Manual | SEM_WAIT(3) |
sem_wait, sem_timedwait,
sem_trywait —
#include <semaphore.h>
int
sem_wait(sem_t
*sem);
int
sem_timedwait(sem_t
*sem, const struct
timespec * restrict abstime);
int
sem_trywait(sem_t
*sem);
sem_wait() function decrements (locks) the semaphore
pointed to by sem, but blocks if the value of
sem is zero, until the value is non-zero and the value
can be decremented.
The sem_timedwait() function performs the
same action, but will not wait beyond abstime for the
value of sem to be non-zero.
The sem_trywait() function decrements
(locks) the semaphore pointed to by sem only if the
value is non-zero. Otherwise, the semaphore is not decremented and an error
is returned.
sem_wait() function returns the value 0 if
successful; otherwise the value -1 is returned and the global variable
errno is set to indicate the error.
sem_wait(), sem_timedwait(), and
sem_trywait() will fail if:
EINVAL]Additionally, sem_trywait() will fail
if:
EAGAIN]sem_timedwait() will also fail if:
ETIMEDOUT]sem_wait() and sem_trywait()
conform to ISO/IEC 9945-1:1996
(“POSIX.1”).
| February 29, 2012 | NetBSD 9.2 |