Click this button to go to the index for this section.

msem_init(3)
NAME
  msem_init - Initializes a semaphore in a mapped file or shared memory
  region

LIBRARY
  Standard C Library (libc.a)

SYNOPSIS
  #include <sys/mman.h>
  msemaphore *msem_init (
	  msemaphore *sem,
	  int initial_value );

PARAMETERS
  sem	    Points to an msemaphore structure in which the state of the
	    semaphore is stored.

  initial_value
	    Determines whether the semaphore is locked or unlocked at
	    allocation.

DESCRIPTION
  The msem_init() function allocates a new binary semaphore and initializes
  the state of the new semaphore.

  If the initial_value parameter is MSEM_LOCKED, the new semaphore is
  initialized in the locked state.  If the initial_value parameter is
  MSEM_UNLOCKED, the new semaphore is initialized in the unlocked state.

  The msemaphore structure is located within a mapped file or shared memory
  region created by a successful call to the mmap() function and having both
  read and write access.

  If a semaphore is created in a mapped file region, any reference by a
  process which has mapped the same file, using a (struct msemaphore *)
  pointer which resolves to the same file offset, is taken as a reference to
  the same semaphore.  If a semaphore is created in an anonymous shared
  memory region, any reference by a process which shares the same region,
  using a (struct msemaphore *) pointer which resolves to the same offset
  from the start of the region, is taken as a reference to the same
  semaphore.

  Any previous semaphore state stored in the msemaphore structure is ignored
  and overwritten.

NOTES
  AES Support Level:
		 Trial use

RETURN VALUES
  Upon successful completion, the msem_init() function returns a pointer to
  the initialized msemaphore structure.	 On error, the msem_init() function
  returns null and sets errno to indicate the error.

ERRORS
  If the msem_init() function fails, errno may be set to one of the following
  values:

  [EINVAL]  The initial_value parameter is not valid.

  [ENOMEM]  A new semaphore could not be created.

RELATED INFORMATION
  Functions: mmap(2), msem_lock(3), msem_remove(3), msem_unlock(3)