Name

sync — commit buffer cache to disk

Synopsis

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

DESCRIPTION

sync() first commits inodes to buffers, and then buffers to disk.

ERRORS

This function is always successful.

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001.

NOTES

Since glibc 2.2.2 the Linux prototype 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 2.79 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


Copyright (c) 1992 Drew Eckhardt (drewcs.colorado.edu), March 28, 1992

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.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

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manual page may be incorrect or out-of-date.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
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
professionally.

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.

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.