FreeBSD manual
download PDF document: sem_init.3.pdf
SEM_INIT(3) FreeBSD Library Functions Manual SEM_INIT(3)
NAME
sem_init - initialize an unnamed semaphore
LIBRARY
Standard C Library (libc, -lc)
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, the semaphore should be located in shared
memory region (see mmap(2), shm_open(2), and shmget(2)), any process
having read and write access to address sem can perform semaphore
operations on sem.
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 The sem argument is no longer valid after a successful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
The sem_init() function returns the value 0 if successful; otherwise the
value -1 is returned and the global variable errno is set to indicate the
error.
ERRORS
The sem_init() function will fail if:
[EINVAL] The value argument exceeds SEM_VALUE_MAX.
[ENOSPC] Memory allocation error.
SEE ALSO
sem_destroy(3), sem_getvalue(3), sem_post(3), sem_trywait(3), sem_wait(3)
STANDARDS
The sem_init() function conforms to ISO/IEC 9945-1:1996 ("POSIX.1").
FreeBSD 14.0-RELEASE-p6 January 9, 2010 FreeBSD 14.0-RELEASE-p6