sem_init(3C) Standard C Library Functions sem_init(3C)NAMEsem_init - initialize an unnamed semaphore
SYNOPSIS
#include <semaphore.h>
int sem_init(sem_t *sem, int pshared, unsigned int value);
DESCRIPTION
The sem_init() function is used to initialize the unnamed semaphore
referred to by sem. The value of the initialized semaphore is value.
Following a successful call to sem_init(), the semaphore may be used in
subsequent calls to sem_wait(3C), sem_trywait(3C), sem_post(3C), and
sem_destroy(3C). This semaphore remains usable until the semaphore is
destroyed.
If the pshared argument has a non-zero value, then the semaphore is
shared between processes; in this case, any process that can access the
semaphore sem can use sem for performing sem_wait(3C), sem_trywait(3C),
sem_post(3C), and sem_destroy(3C) operations.
Only sem itself may be used for performing synchronization. The result
of referring to copies of sem in calls to sem_wait(3C), sem_try‐
wait(3C), sem_post(3C), and sem_destroy(3C), is undefined.
If the pshared argument is zero, then the semaphore is shared between
threads of the process; any thread in this process can use sem for per‐
forming sem_wait(3C), sem_trywait(3C), sem_post(3C), and
sem_destroy(3C) operations. The use of the semaphore by threads other
than those created in the same process is undefined.
Attempting to initialize an already initialized semaphore results in
undefined behavior.
The sem_open(3C) function is used with named semaphores.
RETURN VALUES
Upon successful completion, the function initializes the semaphore in
sem. Otherwise, it returns −1 and sets errno to indicate the error.
ERRORS
The sem_init() function will fail if:
EINVAL The value argument exceeds SEM_VALUE_MAX.
ENOSPC A resource required to initialize the semaphore has been
exhausted, or the resources have reached the limit on sema‐
phores (SEM_NSEMS_MAX).
ENOSYS The sem_init() function is not supported by the system.
EPERM The process lacks the appropriate privileges to initialize
the semaphore.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ATTRIBUTE TYPE │ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Committed │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
├─────────────────────────────┼─────────────────────────────┤
│Standard │See standards(5). │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOsem_destroy(3C), sem_open(3C), sem_post(3C), sem_wait(3C),
attributes(5), standards(5)SunOS 5.11 9 Jul 2009 sem_init(3C)