SYNC(2) Linux Programmer's Manual SYNC(2)
sync, syncfs - commit buffer cache to disk
int syncfs(int fd);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
sync() 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 containing file referred to
by the open file descriptor fd.
syncfs() returns 0 on success; on error, it returns -1 and sets errno to indicate the
sync() is always successful.
syncfs() can fail for at least the following reason:
EBADF fd is not a valid file descriptor.
syncfs() first appeared in Linux 2.6.39; library support was added to glibc in version
sync(): SVr4, 4.3BSD, POSIX.1-2001.
syncfs() is Linux-specific.
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.
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
bdflush(2), fdatasync(2), fsync(2), sync(8), update(8)
This page is part of release 3.53 of the Linux man-pages project. A description of the
project, and information about reporting bugs, can be found at
Linux 2012-05-04 SYNC(2)