sem(4) [netbsd man page]

SEM(4)							   BSD Kernel Interfaces Manual 						    SEM(4)

NAME

     sem -- POSIX semaphores

SYNOPSIS

     To link into the kernel:

	   options P1003_1B_SEMAPHORE

DESCRIPTION

     The sem facility provides system calls used by the standard C library (libc) to implement POSIX semaphores.

SEE ALSO

     config(1), sem_destroy(3), sem_getvalue(3), sem_init(3), sem_open(3), sem_post(3), sem_wait(3), options(4)

HISTORY

     The sem facility appeared as a kernel option in NetBSD 2.0.

BUGS

     The current implementation does not support shared, unnamed semaphores.

BSD
								 January 21, 2005							       BSD

SEM_INIT(3)						   BSD 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 opera-
     tions 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  The sem argument is no longer valid after a successful call to sem_destroy(3).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 indi-
     cate 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'').

BSD
								  January 9, 2010							       BSD