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

SYNOPSIS
  #include <sys/mman.h>

  msemaphore *msem_init(
	  msemaphore *sem ,
	  int initial_value );

LIBRARY
  Standard C Library (libc)

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.

SEE ALSO
  Functions: mmap(2), msem_lock(3), msem_remove(3), msem_unlock(3)

Index for Section 3

Alphabetical listing for M

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