'\"macro stdmacro
.if n .pH g2.msync @(#)msync	40.15 of 1/3/91
.\" Copyright 1991 UNIX System Laboratories, Inc.
.\" Copyright 1989, 1990 AT&T
'\" ident	"@(#)svid_rt:rt_os/msync	1.2"
.\" @(#)msync 1.4 88/09/26 SMI;
'\"macro stdmacro
.\" Sun's msync.3
.nr X
.if \nX=0 .ds x} msync 2 "" "\&"
.if \nX=1 .ds x} msync 2 ""
.if \nX=2 .ds x} msync 2 "" "\&"
.if \nX=3 .ds x} msync "" "" "\&"
.TH \*(x}
.SH NAME
\f4msync\f1 \- synchronize memory with physical storage
.SH SYNOPSIS
.ft 4
.nf
#include <sys/types.h>
#include <sys/mman.h>
.sp0.5
int msync(void \(**addr, size_t len, int flags);
.ft 1
.fi
.SH DESCRIPTION
The function \f4msync\f1
writes all modified copies of pages over the range
[\f2addr, addr + len\f1\^)
to their backing storage locations.
\f4msync\f1
optionally invalidates any copies so that further references to the pages
will be obtained by the system from their backing
storage locations.
The backing storage for a modified \f4MAP_SHARED\fP mapping is the file
the page is mapped to;
the backing storage for a modified \f4MAP_PRIVATE\fP mapping is its swap area.
.P
\f2flags\f1
is a bit pattern built from the following values:
.P
.RS
.ta 25n 30n
.nf
\f4MS_ASYNC\f1	perform asynchronous writes
\f4MS_SYNC\f1	perform synchronous writes
\f4MS_INVALIDATE\f1	invalidate mappings
.fi
.RE
.P
If \f4MS_ASYNC\f1 is set, \f4msync\fP returns immediately once all write operations are scheduled;
if \f4MS_SYNC\f1 is set, \f4msync\fP does not return until all write operations are completed.
.P
\f4MS_INVALIDATE\f1 invalidates all cached copies of data in memory,
so that further references to the pages will be obtained by the system from
their backing storage locations.
.P
\f2msync\fP will fail if:
.TP 15
.SM
\%[EINVAL]
If \f2addr\fP is not a multiple of the page size as returned by
\f4sysconf\fP(3C).
.TP
.SM
\%[EIO]
An I/O error occurred while reading from or writing to the file system.
.TP
.SM
\%[ENOMEM]
Addresses in the range (\f2addr, addr + len\fP\^) 
are outside the valid range for the address space of a process or
pages not mapped are specified.
.TP
.SM
\%[EBUSY]
.SM
.B MS_INVALIDATE
was specified and one or more of the pages
was locked in memory.
.SH SEE ALSO
\f4mmap\fP(2),
\f4mpin\fP(2),
\f4sysconf\fP(3C).
.SH DIAGNOSTICS
Upon successful completion, the function \f4msync\f1 returns
0; otherwise, it returns \-1 and 
sets \f4errno\f1 to indicate the error.
.SH NOTES
\f4msync\f1
should be used by programs that require a memory object to
be
in a known state, for example, in building transaction facilities.