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msync(2)
NAME
  msync - Synchronize a mapped file

SYNOPSIS
  #include <sys/mman.h>

  int msync(
	  void *addr,
	  size_t len,
	  int flags );

  The following function declaration does not conform to current industry
  standards and is supported only for backward compatibility:

  #include <sys/types.h>
  #include <sys/mman.h>

  int msync(
	  caddr_t addr,
	  size_t len,
	  int flags );

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  msync(): XSH4.2, XSH5.0

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  addr	  Specifies the starting address of the region to be synchronized.

  len	  Specifies the length in bytes of the region to be synchronized.
	  This parameter must be a multiple of the page size as returned by
	  sysconf(_SC_PAGE_SIZE).  If len is not a multiple of the page size
	  as returned by sysconf(_SC_PAGE_SIZE), the length of the region
	  will be rounded up to the next multiple of the page size.

  flags	  Specifies one of the following symbolic constants defined in the
	  <sys/mman.h> file:

	  MS_ASYNC
		  Specifies an asynchronous cache flush. The msync() function
		  returns after the system schedules all write operations.

	  MS_SYNC Specifies a synchronous cache flush. The msync() function
		  returns after the system completes all write operations.

	  MS_INVALIDATE
		  Specifies invalidating all cached pages. New copies of the
		  pages must be obtained from the file system the next time
		  they are referenced.

DESCRIPTION
  The msync() function controls the caching operations of a mapped file
  region. The msync() function can be used to ensure that modified pages in
  the region are transferred to the file's underlying storage device.
  (However, normal system activity can cause pages to be written to a storage
  device, so there is no guarantee that a call to the msync() function is the
  only control over when pages are written.) You can also use the function to
  control the visibility of modifications with respect to file system
  operations.

  After a successful call to the msync() function with the flags parameter
  set to MS_SYNC, all previous modifications to the mapped region are visible
  to processes using the read() function. Previous modifications to the file
  using the write() function might be lost.

  After a successful call to the msync() function with the flags parameter
  set to MS_INVALIDATE, all previous modifications to the file using the
  write() function are visible to the mapped region. Previous direct
  modifications to the mapped region might be lost.

RETURN VALUES
  Upon successful completion, the msync() function returns 0 (zero).
  Otherwise, the msync() function returns -1 and sets errno to indicate the
  error.

ERRORS
  The msync() function sets errno to the specified values for the following
  conditions:

  [EBUSY] Some or all of the addresses in the range starting at addr and
	  continuing for len bytes are locked, and MS_INVALIDATE is
	  specified.

  [EFAULT]
	  [Tru64 UNIX]	The range [addr, addr + len) includes an invalid
	  address.

  [EINVAL]
	  One of the following conditions applies:

	    ·  The addr parameter is not a multiple of the page size as
	       returned by sysconf(_SC_PAGE_SIZE).

	    ·  The flags parameter is invalid.

  [EIO]	  [Tru64 UNIX]	An I/O error occurred while reading from or writing
	  to the file system.

  [ENOMEM]
	  The range specified by [addr, addr + len) is invalid for a process'
	  address space, or the range specifies one or more unmapped pages.

SEE ALSO
  Functions: fsync(2), mmap(2), read(2), write(2), sysconf(3)

  Standards: standards(5)

Index for Section 2

Alphabetical listing for M

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