Linux.com

msync.2

MSYNC

Section: Linux Programmer's Manual (2)
Updated: 2008-04-22
Index Return to Main Contents
 

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 corresponds 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 3.21 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/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
AVAILABILITY
SEE ALSO
COLOPHON

 

Comments

Subscribe to Comments Feed

Upcoming Linux Foundation Courses

  1. LFD211 Introduction to Linux for Developers
    08 Dec » 09 Dec - Virtual
    Details
  2. LFS220 Linux System Administration
    08 Dec » 11 Dec - Virtual
    Details
  3. LFD331 Developing Linux Device Drivers
    15 Dec » 19 Dec - Virtual
    Details

View All Upcoming Courses

Become an Individual Member
Check out the Friday Funnies

Sign Up For the Linux.com Newsletter


Who we are ?

The Linux Foundation is a non-profit consortium dedicated to the growth of Linux.

More About the foundation...

Frequent Questions

Join / Linux Training / Board