msync(2) [mojave man page]

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NAME

     msync -- synchronize a mapped region

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/mman.h>

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

DESCRIPTION

     The msync() system call writes modified whole pages back to the filesystem and updates the file modification time.  Only those pages contain-
     ing addr and len-1 succeeding locations will be examined.

     The flags argument may be specified as follows:

     MS_ASYNC	     Return immediately
     MS_SYNC	     Perform synchronous writes
     MS_INVALIDATE   Invalidate all cached data

     The MS_ASYNC flag is not permitted to be combined with other flags.

RETURN VALUES

     If any errors occur, -1 is returned and errno is set to indicate the error.  Otherwise, a 0 value is returned.

ERRORS

     msync() will fail if:

     [EBUSY]		Some of the specified addresses are locked and MS_INVALIDATE is specified.

     [EINVAL]		addr is not a multiple of the hardware page size.

     [EINVAL]		len is too large, or less than 1.

     [EINVAL]		flags is invalid (e.g., it combines MS_ASYNC with another flag, which is not permitted).

     [EIO]		An I/O error occurs while writing to the file system.

     [ENOMEM]		The specified address range is outside of the address range of the process or includes an unmapped page.

LEGACY SYNOPSIS

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

     The include file <sys/types.h> is necessary.

SEE ALSO

     madvise(2), mincore(2), mprotect(2), munmap(2), compat(5)

HISTORY

     The msync() function first appeared in 4.4BSD.

BSD
								   June 21, 1994							       BSD

MSYNC(2)						     Linux Programmer's Manual							  MSYNC(2)

NAME

       msync - synchronize a file with a memory map

SYNOPSIS

       #include <sys/mman.h>

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

DESCRIPTION

       msync()	flushes  changes  made	to the in-core copy of a file that was mapped into memory using mmap(2) back to disk.  Without use of this
       call there is no guarantee that changes are written back before munmap(2) is called.  To be more precise, the part of the file that  corre-
       sponds to the memory area starting at addr and having length length is updated.

       The  flags argument may have the bits MS_ASYNC, MS_SYNC, and MS_INVALIDATE set, but not both MS_ASYNC and MS_SYNC.  MS_ASYNC specifies that
       an update be scheduled, but the call returns immediately.  MS_SYNC asks for an update and waits for it to complete.  MS_INVALIDATE asks	to
       invalidate other mappings of the same file (so that they can be updated with the fresh values just written).

RETURN VALUE

       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS

       EBUSY  MS_INVALIDATE was specified in flags, and a memory lock exists for the specified address range.

       EINVAL addr  is	not  a multiple of PAGESIZE; or any bit other than MS_ASYNC | MS_INVALIDATE | MS_SYNC is set in flags; or both MS_SYNC and
	      MS_ASYNC are set in flags.

       ENOMEM The indicated memory (or part of it) was not mapped.

CONFORMING TO

       POSIX.1-2001.

       This call was introduced in Linux 1.3.21, and then used EFAULT instead of ENOMEM.  In Linux 2.4.19 this was  changed  to  the  POSIX  value
       ENOMEM.

AVAILABILITY

       On  POSIX  systems  on which msync() is available, both _POSIX_MAPPED_FILES and _POSIX_SYNCHRONIZED_IO are defined in <unistd.h> to a value
       greater than 0.	(See also sysconf(3).)

SEE ALSO

       mmap(2)

       B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128-129 and 389-391.

COLOPHON

       This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

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