Linux manual pages Section 2  

Name

sync, syncfs — commit buffer cache to disk

Synopsis

#include <unistd.h>
void sync( void);  
 
void syncfs( int fd);
 
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sync():
_BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
syncfs():
_GNU_SOURCE

DESCRIPTION

sync() causes all buffered modifications to file metadata and data to be written to the underlying file systems.

syncfs() is like sync(), but synchronizes just the file system containing file referred to by the open file descriptor fd.

RETURN VALUE

syncfs() returns 0 on success; on error, it returns −1 and sets errno to indicate the error.

ERRORS

sync() is always successful.

syncfs() can fail for at least the following reason:

EBADF

fd is not a valid file descriptor.

VERSIONS

syncfs() first appeared in Linux 2.6.39.

CONFORMING TO

sync(): SVr4, 4.3BSD, POSIX.1-2001.

syncfs() is Linux-specific.

NOTES

Since glibc 2.2.2 the Linux prototype for sync() is as listed above, following the various standards. In libc4, libc5, and glibc up to 2.2.1 it was "int sync(void)", and sync() always returned 0.

BUGS

According to the standard specification (e.g., POSIX.1-2001), sync() schedules the writes, but may return before the actual writing is done. However, since version 1.3.20 Linux does actually wait. (This still does not guarantee data integrity: modern disks have large caches.)

SEE ALSO

bdflush(2), fdatasync(2), fsync(2), sync(8), update(8)

COLOPHON

This page is part of release 3.33 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man-pages/.


Copyright (c) 1992 Drew Eckhardt (drewcs.colorado.edu), March 28, 1992
and Copyright (c) 2011 Michael Kerrisk <mtk.manpagesgmail.com>

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

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manual under the conditions for verbatim copying, provided that the
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Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
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Formatted or processed versions of this manual, if unaccompanied by
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Modified by Michael Haardt <michaelmoria.de>
Modified Sat Jul 24 12:02:47 1993 by Rik Faith <faithcs.unc.edu>
Modified 15 Apr 1995 by Michael Chastain <mecshell.portal.com>:
  Added reference to `bdflush(2)'.
Modified 960414 by Andries Brouwer <aebcwi.nl>:
  Added the fact that since 1.3.20 sync actually waits.
Modified Tue Oct 22 22:27:07 1996 by Eric S. Raymond <esrthyrsus.com>
Modified 2001-10-10 by aeb, following Michael Kerrisk.
2011-09-07, mtk, Added syncfs() documentation,