msync man page on Manjaro

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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 mun‐
       map(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_INVALI‐
       DATE  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).)

NOTES
       According to POSIX, either MS_SYNC or MS_ASYNC  must  be	 specified  in
       flags,  and  indeed  failure  to	 include one of these flags will cause
       msync() to fail on some systems.	 However,  Linux  permits  a  call  to
       msync()	that specifies neither of these flags, with semantics that are
       (currently) equivalent to specifying MS_ASYNC.	(Since	Linux  2.6.19,
       MS_ASYNC	 is  in	 fact  a no-op, since the kernel properly tracks dirty
       pages and flushes them to storage as necessary.)	  Notwithstanding  the
       Linux  behavior, portable, future-proof applications should ensure that
       they specify either MS_SYNC or MS_ASYNC in flags.

SEE ALSO
       mmap(2)

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

COLOPHON
       This page is part of release 3.65 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/.

Linux				  2014-04-20			      MSYNC(2)
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