SYNC
Section: Linux Programmer's Manual (2)
Updated: 2017-09-15
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NAME
sync, syncfs - commit filesystem caches to disk
SYNOPSIS
#include <unistd.h>
void sync(void);
int syncfs(int fd);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
sync():
-
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE
syncfs():
-
_GNU_SOURCE
DESCRIPTION
sync()
causes all pending modifications to filesystem metadata and cached file
data to be written to the underlying filesystems.
syncfs()
is like
sync(),
but synchronizes just the filesystem 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;
library support was added to glibc in version 2.14.
CONFORMING TO
sync():
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
syncfs()
is Linux-specific.
NOTES
Since glibc 2.2.2, the Linux prototype for
sync()
is as listed above,
following the various standards.
In glibc 2.2.1 and earlier,
it was "int sync(void)", and
sync()
always returned 0.
According to the standard specification (e.g., POSIX.1-2001),
sync()
schedules the writes, but may return before the actual
writing is done. However Linux waits for I/O completions,
and thus
sync()
or
syncfs()
provide the same guarantees as fsync called on every file in
the system or filesystem respectively.
BUGS
Before version 1.3.20 Linux did not wait for I/O to complete
before returning.
SEE ALSO
sync(1),
fdatasync(2),
fsync(2)
COLOPHON
This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- CONFORMING TO
-
- NOTES
-
- BUGS
-
- SEE ALSO
-
- COLOPHON
-
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