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msync(2) [redhat man page]

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

msync - synchronize a file with a memory map SYNOPSIS
#include <unistd.h> #include <sys/mman.h> #ifdef _POSIX_MAPPED_FILES #ifdef _POSIX_SYNCHRONIZED_IO int msync(const void *start, size_t length, int flags); #endif #endif 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 start 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
EINVAL start is not a multiple of PAGESIZE, or any bit other than MS_ASYNC | MS_INVALIDATE | MS_SYNC is set in flags. EFAULT The indicated memory (or part of it) was not mapped. CONFORMING TO
POSIX.1b (formerly POSIX.4) SEE ALSO
mmap(2), B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128-129 and 389-391. Linux 1.3.86 1996-04-12 MSYNC(2)

Check Out this Related Man Page

MSYNC(2)						      BSD System Calls Manual							  MSYNC(2)

msync -- synchronize a mapped region LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/types.h> #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: [EINVAL] addr is not a multiple of the hardware page size. [EINVAL] len is too large, or less than 1. [EINVAL] flags combined MS_ASYNC with another flag, which is not permitted. [EIO] An I/O error occurred while writing to the file system. SEE ALSO
madvise(2), mincore(2), mprotect(2), munmap(2) HISTORY
The msync() function first appeared in 4.4BSD. BSD
June 21, 1994 BSD

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