sem_init(3C)                                                      sem_init(3C)


NAME
     sem_init - initialize a posix unnamed semaphore

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

DESCRIPTION
     sem_init initializes the unnamed semaphore located at address sem.  The
     address sem may reside anywhere in the calling processes address space,
     but if the semaphore is intended to be shared across process boundaries,
     sem must reside in shared memory.

     The pshared argument is used to specify whether the semaphore is intended
     to be shared across process boundaries or only used locally by threads of
     execution within a common process.  If pshared is set to zero, then the
     semaphore is not intended for sharing across process boundaries.
     Conversely, a non-zero pshared value indicates any process having read
     and write access to address sem, may perform semaphore operations on sem.
     Unnamed semaphores have been optimized for local thread usage, delivering
     increased performance within posix thread applications [see
     pthread_create(3P)].

     The initial value of the semaphore is specified by value, which may be
     any non-negative number less than {SEM_VALUE_MAX} [see sysconf(3C)].

     POSIX semaphores are compatible across all MIPS ABIs: o32, n32 and 64.

     Once a semaphore is initialized, processes may execute the following
     semaphore operations: sem_post, sem_wait, sem_trywait, sem_getvalue,
     sem_destroy.

     sem_init will fail if one or more of the following are true:

     [EINVAL]    The value parameter was set to a number greater than
                 {SEM_VALUE_MAX}.

     [ENOSPC]    The resources required to initialize the semaphore have been
                 depleted.

     [EPERM]     The calling process lacks the permissions required to
                 initialize the semaphore.

SEE ALSO
     sem_destroy(3C), sem_getvalue(3C), sem_post(3C), sem_wait(3C),
     sem_trywait(3C), sem_open(3C), sem_close(3C), sem_unlink(3C),
     shm_open(3C), sysconf(3C), mmap(3C)


DIAGNOSTICS
     Upon successful completion, a value of 0 is returned to the calling
     process. Otherwise, a value of -1 is returned and errno is set to
     indicate the error.


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