mirror of https://github.com/mkerrisk/man-pages
112 lines
3.2 KiB
Groff
112 lines
3.2 KiB
Groff
.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" Copyright (C) 1996 Andries Brouwer (aeb@cwi.nl)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH MSYNC 2 2003-08-21 "Linux 2.4" "Linux Programmer's Manual"
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.SH NAME
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msync \- synchronize a file with a memory map
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.SH SYNOPSIS
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.B #include <sys/mman.h>
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.sp
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.BI "int msync(void *" start ", size_t " length ", int " flags );
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.SH DESCRIPTION
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.BR msync ()
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flushes changes made to the in-core copy of a file that was mapped
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into memory using
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.BR mmap (2)
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back to disk.
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Without use of this call
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there is no guarantee that changes are written back before
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.BR munmap (2)
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is called.
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To be more precise, the part of the file that
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corresponds to the memory area starting at
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.I start
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and having length
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.I length
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is updated.
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The
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.I flags
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argument may have the bits
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.BR MS_ASYNC ,
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.BR MS_SYNC ,
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and
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.B MS_INVALIDATE
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set, but not both
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.B MS_ASYNC
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and
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.BR MS_SYNC .
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.B MS_ASYNC
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specifies that an update be scheduled, but the call
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returns immediately.
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.B MS_SYNC
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asks for an update and waits for it to complete.
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.B MS_INVALIDATE
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asks to invalidate other mappings of the same file
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(so that they can be updated with the fresh values just written).
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.SH "RETURN VALUE"
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On success, zero is returned.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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.TP
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.BR EBUSY
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MS_INVALIDATE was specified in
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.IR flags ,
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and a memory lock exists for the specified address range.
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.TP
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.BR EINVAL
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.I start
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is not a multiple of PAGESIZE; or any bit other than
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MS_ASYNC | MS_INVALIDATE | MS_SYNC is set in
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.IR flags ;
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or both
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MS_SYNC and MS_ASYNC are set in
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.IR flags .
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.TP
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.B ENOMEM
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The indicated memory (or part of it) was not mapped.
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.SH AVAILABILITY
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On POSIX systems on which
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.BR msync ()
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is available, both
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.B _POSIX_MAPPED_FILES
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and
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.B _POSIX_SYNCHRONIZED_IO
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are defined in <unistd.h> to a value greater than 0. (See also
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.BR sysconf (3).)
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.\" POSIX.1-2001: It shall be defined to -1 or 0 or 200112L.
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.\" -1: unavailable, 0: ask using sysconf().
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.\" glibc defines them to 1.
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.SH "CONFORMING TO"
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POSIX.1-2001.
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This call was introduced in Linux 1.3.21, and then used EFAULT instead of
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ENOMEM. In Linux 2.4.19 this was changed to the POSIX value ENOMEM.
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.SH "SEE ALSO"
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.BR mmap (2)
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.br
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B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128-129 and 389-391.
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