SEM_INIT(3) BSD Library Functions Manual SEM_INIT(3)
NAME
sem_init -- initialize an unnamed semaphore
LIBRARY
POSIX Real-time Library (librt, -lrt)
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, sem_trywait, sem_post, and
sem_destroy. sem is no longer valid after a successful call to sem_destroy.
RETURN VALUES
The sem_init() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indi-
cate the error.
ERRORS
sem_init() 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)
STANDARDS
sem_init() conforms to ISO/IEC 9945-1:1996 (``POSIX.1'').
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.
BSD
January 22, 2003 BSD
