SEM_INIT(3)

NAME
sem_init - initialize an unnamed semaphore

LIBRARY
libc

SYNOPSIS
#include <semaphore.h>
int
sem_init(sem_t *sem, int pshared, unsigned int value);

DESCRIPTION
The sem_init() function initializes the unnamed semaphore pointed to by sem to have the value value. A non-zero value for pshared specifies a shared semaphore that can be used by multiple processes, which this implementation is not capable of.

Following a successful call to sem_init(), sem can be used as an argument in subsequent calls to sem_wait(3), sem_trywait(3), sem_post(3), and sem_destroy(3). The sem argument is no longer valid after a successful call to sem_destroy(3).

RETURN VALUES

ERRORS
The sem_init() function will fail if:

[EINVAL]
    value exceeds SEM_VALUE_MAX.

[ENOSPC]
    Memory allocation error.

[EPERM]
    Unable to initialize a shared semaphore.

SEE ALSO
sem_destroy(3), sem_post(3), sem_trywait(3), sem_wait(3), sem(4)

STANDARDS
The sem_init() function conforms to p1003.1-96.

This implementation does not support shared semaphores, and reports this fact by setting errno to EPERM. This is perhaps a stretch of the intention of POSIX, but is compliant, with the caveat that sem_init() always reports a permissions error when an attempt to create a shared semaphore is made.