MSYNC(2) BSD System Calls Manual MSYNC(2)NAMEmsync — 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 all pages with shared modifications in the
specified region of the process's address space back to permanent stor‐
age, and, if requested, invalidates cached data mapped in the region. If
len is 0, all modified pages within the region containing addr will be
flushed; if len is non-zero, only modified pages containing addr and len
succeeding locations will be flushed. Any required synchronization of
memory caches will also take place at this time. Filesystem operations
on a file that is mapped for shared modifications are unpredictable
except after an msync().
The flags argument is formed by or'ing the following values
MS_ASYNC Perform asynchronous writes.
MS_SYNC Perform synchronous writes.
MS_INVALIDATE Invalidate cached data after writing.
RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
ERRORS
The following errors may be reported:
[EBUSY] The MS_INVALIDATE flag was specified and a portion of
the specified region was locked with mlock(2).
[EINVAL] The specified flags argument was invalid.
[EINVAL] The addr parameter was not page aligned.
[EINVAL] The addr parameter did not specify an address part of
a mapped region.
[EINVAL] The len parameter was negative.
[EIO] An I/O error occurred while writing to the file sys‐
tem.
[ENOMEM] Addresses in the specified region are outside the
range allowed for the address space of the process, or
specify one or more pages which are unmapped.
SEE ALSOmlock(2), mmap(2), munlock(2)STANDARDS
The msync() function conforms to IEEE Std 1003.1b-1993 (“POSIX.1”)
HISTORY
The msync() function first appeared in 4.4BSD. It was modified to con‐
form to IEEE Std 1003.1b-1993 (“POSIX.1”) in NetBSD 1.3.
BSD October 17, 2005 BSD
