sem_init() -- initialize an unnamed semaphore

SYNOPSIS

#include <semaphore.h>

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

The sem_init() function initializes the unnamed semaphore specified by the sem argument and assigns that semaphore the value specified by the value argument. Once the semaphore has been successfully initializes, you can use it in subsequent calls to sem_wait(), sem_trywait(), sem_post(), and sem_destroy(). You can continue to use the semaphore until it is destroyed with the sem_destroy() function.

If you attempt to initialize a semaphore that has already been initialized, the original semaphore is overwritten by the newly initialized one.

You can only use sem itself to perform synchronization. Referring to copies of sem in calls to the sem_wait(), sem_trywait(), sem_post(), and sem_destroy() functions is not recommended. While the current implementation of the semaphore functions supports the use of copies, there is no guarantee that future implementations will have this support.

Semaphores created with sem_init() should only be destroyed with the sem_destroy() function and semaphores created with sem_open() should only be closed with the sem_close() function.

PARAMETERS

sem: Specifies the semaphore to be initialized.
pshared: Is ignored. In other implementations, this argument specifies whether or not the newly initialized semaphore is shared between processes or between threads. A non-zero value means the semaphore is shared between processes; a value of zero means it is shared between threads. On the NuTCRACKER Platform, semaphores are always shared.
value: Specifies the value to assign to the newly initialized semaphore.

RETURN VALUES

When successful, the sem_init() function initializes the specified semaphore . Otherwise, it returns -1 and sets errno to one of the following values:

EACCES: The process lacks the appropriate privileges to initialize the semaphore.
EEXIST: The specified semaphore already exists.
EINVAL: The value argument exceeds SEM_VALUE_MAX.
ENFILE: Too many semaphores are currently open in the system.
ENOSPC: A resource required to initialize the semaphore has been exhausted, or the limit on semaphores (SEM_NSEMS_MAX) has been reached.

sem_init()
initialize an unnamed semaphore

Realtime Function

SYNOPSIS

DESCRIPTION

PARAMETERS

RETURN VALUES

EXAMPLES

CONFORMANCE

MULTITHREAD SAFETY LEVEL

PORTING ISSUES

AVAILABILITY

SEE ALSO

sem_init() initialize an unnamed semaphore

Realtime Function

sem_init()
initialize an unnamed semaphore