msync
—
synchronize a mapped region
Standard C Library (libc, -lc)
#include <sys/mman.h>
int
msync
(void
*addr, size_t len,
int flags);
The msync
() system call writes all pages with shared
modifications in the specified region of the process's address space back to
permanent storage, 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
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1
is returned and errno is set to indicate the error.
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.
- [
EIO
]
- An I/O error occurred while writing to the file system.
- [
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.
The msync
() function conforms to IEEE
Std 1003.1b-1993 (“POSIX.1b”)
The msync
() function first appeared in
4.4BSD. It was modified to conform to
IEEE Std 1003.1b-1993 (“POSIX.1b”) in
NetBSD 1.3.