sem_init(3RT) Realtime Library Functions sem_init(3RT)NAMEsem_init - initialize an unnamed semaphore
SYNOPSIS
cc [ flag... ] file... -lrt [ library... ]
#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(3RT), sem_trywait(3RT), sem_post(3RT), and
sem_destroy(3RT). 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(3RT), sem_try‐
wait(3RT), sem_post(3RT), and sem_destroy(3RT) operations.
Only sem itself may be used for performing synchronization. The result
of referring to copies of sem in calls to sem_wait(3RT), sem_try‐
wait(3RT), sem_post(3RT), and sem_destroy(3RT), 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(3RT), sem_trywait(3RT), sem_post(3RT), and
sem_destroy(3RT) 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.
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 semaphores (SEM_NSEMS_MAX).
ENOSYS The sem_init() function is not supported by the system.
EPERM The process lacks the appropriate privileges to ini‐
tialize the semaphore.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOsem_destroy(3RT), sem_post(3RT), sem_wait(3RT), attributes(5), stan‐
dards(5)SunOS 5.10 28 Jun 2002 sem_init(3RT)
