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SYNC(2) Linux Programmer's Manual SYNC(2)
NAME
sync, syncfs - commit buffer cache 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():
_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 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(): 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 vari‐
ous standards. In glibc 2.2.1 and earlier, 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(1)
COLOPHON
This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.
Linux 2014-08-19 SYNC(2)
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