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Name

sem_init - initialize an unnamed semaphore

Synopsis

cc [ flag ... ] file ... -lposix4 [ library ... ]

#include <semaphore.h>

int sem_init(sem_t *sem, int pshared, unsigned int value );

typedef struct {
...

} sem_t; /*opaque POSIX.4 semaphore*/

MT-Level

MT-Safe

Description

sem_init() is used to initialize the unnamed semaphore, referred to by sem, to value. This semaphore may be used in subsequent calls to sem_wait(3R) , sem_trywait(3R) , sem_post(3R) , and sem_destroy(3R) . This semaphore remains usable until the semaphore is destroyed.

If pshared is non-zero, then the semaphore is sharable between processes. If the semaphore is not being shared between processes, the application should set pshared to 0.

Return Values

If successful, sem_init() returns 0 and initializes the semaphore in sem; otherwise it returns -1 and sets errno to indicate the error condition.

Errors

EINVAL
value exceeds SEM_VALUE_MAX.
ENOSPC
A resource required to initialize the semaphore has been exhausted.

The resources have reached the limit on semaphores, SEM_NSEMS_MAX.

ENOSYS
sem_init() is not supported by this implementation.
EPERM
The calling process lacks the appropriate privileges to initialize the semaphore.

See Also

sem_destroy(3R) , sem_post(3R) , sem_wait(3R)

Bugs

In Solaris 2.5, these functions always return -1 and set errno to ENOSYS, because this release does not support the Semaphores option. It is our intention to provide support for these interfaces in future releases.

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