SYNC(2) Linux Programmer's Manual SYNC(2)NAME
sync, syncfs - commit buffer cache to disk
SYNOPSIS
#include <unistd.h>
void sync(void);
void 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
DESCRIPTIONsync() 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 contain‐
ing file referred to by the open file descriptor fd.
RETURN VALUEsyncfs() returns 0 on success; on error, it returns -1 and sets errno
to indicate the error.
ERRORSsync() is always successful.
syncfs() can fail for at least the following reason:
EBADF fd is not a valid file descriptor.
VERSIONSsyncfs() first appeared in Linux 2.6.39.
CONFORMING TOsync(): 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 ALSObdflush(2), fdatasync(2), fsync(2), sync(8), update(8)COLOPHON
This page is part of release 3.35 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/.
Linux 2011-09-07 SYNC(2)
