| .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992 |
| .\" and Copyright (c) 2011 Michael Kerrisk <mtk.manpages@gmail.com> |
| .\" |
| .\" %%%LICENSE_START(VERBATIM) |
| .\" Permission is granted to make and distribute verbatim copies of this |
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| .\" preserved on all copies. |
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| .\" 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| .\" manual page may be incorrect or out-of-date.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. |
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| .\" Formatted or processed versions of this manual, if unaccompanied by |
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| .\" Modified by Michael Haardt <michael@moria.de> |
| .\" Modified Sat Jul 24 12:02:47 1993 by Rik Faith <faith@cs.unc.edu> |
| .\" Modified 15 Apr 1995 by Michael Chastain <mec@shell.portal.com>: |
| .\" Added reference to `bdflush(2)'. |
| .\" Modified 960414 by Andries Brouwer <aeb@cwi.nl>: |
| .\" Added the fact that since 1.3.20 sync actually waits. |
| .\" Modified Tue Oct 22 22:27:07 1996 by Eric S. Raymond <esr@thyrsus.com> |
| .\" Modified 2001-10-10 by aeb, following Michael Kerrisk. |
| .\" 2011-09-07, mtk, Added syncfs() documentation, |
| .\" |
| .TH SYNC 2 2016-03-15 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| sync, syncfs \- commit filesystem caches to disk |
| .SH SYNOPSIS |
| .B #include <unistd.h> |
| .sp |
| .B void sync(void); |
| .sp |
| .BI "int syncfs(int " fd ); |
| .sp |
| .in -4n |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .in |
| .sp |
| .BR sync (): |
| .ad l |
| .RS 4 |
| _XOPEN_SOURCE\ >=\ 500 |
| .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED |
| || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
| || /* Glibc versions <= 2.19: */ _BSD_SOURCE |
| .RE |
| .ad |
| .sp |
| .BR syncfs (): |
| .ad l |
| .RS 4 |
| _GNU_SOURCE |
| .RE |
| .ad |
| .SH DESCRIPTION |
| .BR sync () |
| causes all pending modifications to file system metadata and cached file |
| data to be written to the underlying filesystems. |
| |
| .BR syncfs () |
| is like |
| .BR sync (), |
| but synchronizes just the filesystem containing file |
| referred to by the open file descriptor |
| .IR fd . |
| .SH RETURN VALUE |
| .BR syncfs () |
| returns 0 on success; |
| on error, it returns \-1 and sets |
| .I errno |
| to indicate the error. |
| .SH ERRORS |
| .BR sync () |
| is always successful. |
| |
| .BR syncfs () |
| can fail for at least the following reason: |
| .TP |
| .B EBADF |
| .I fd |
| is not a valid file descriptor. |
| .SH VERSIONS |
| .BR syncfs () |
| first appeared in Linux 2.6.39; |
| library support was added to glibc in version 2.14. |
| .SH CONFORMING TO |
| .BR sync (): |
| POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. |
| |
| .BR syncfs () |
| is Linux-specific. |
| .SH NOTES |
| Since glibc 2.2.2, the Linux prototype for |
| .BR sync () |
| is as listed above, |
| following the various standards. |
| In glibc 2.2.1 and earlier, |
| it was "int sync(void)", and |
| .BR sync () |
| always returned 0. |
| |
| According to the standard specification (e.g., POSIX.1-2001), |
| .BR sync () |
| schedules the writes, but may return before the actual |
| writing is done. However Linux waits for I/O completions, |
| and thus |
| .BR sync () |
| or |
| .BR syncfs () |
| provide the same guarantees as fsync called on every file in |
| the system or filesystem respectively. |
| .SH BUGS |
| Before version 1.3.20 Linux did not wait for I/O to complete |
| before returning. |
| .SH SEE ALSO |
| .BR sync (1), |
| .BR fdatasync (2), |
| .BR fsync (2) |