fsync.2 (2010 09)

f
fsync(2) fsync(2)
NAME
fsync, fdatasync - synchronize a file’s in-core and on-disk states
SYNOPSIS
#include <unistd.h>
int fsync(int fildes);
int fdatasync(int fildes);
DESCRIPTION
fsync() and fdatasync() cause all modified data and attributes of fildes to be moved to a per-
manent storage device. This normally results in all in-core modified copies of buffers for the associated
file to be written to a disk.
fsync() and fdatasync() apply to ordinary files, and apply to block
special devices on systems which permit
I/O
to block special devices.
fsync() and fdatasync() should be used by programs that require a file to be in a known state,
such as when building a simple transaction facility.
fdatasync() causes all modified data and file attributes of fildes required to retrieve the data to be
written to disk.
fsync() causes all modified data and all file attributes of fildes (including access time, modification
time and status change time) to be written to disk.
Together,
fsync() and fdatasync() constitute support for File Synchronization.
RETURN VALUE
fsync() and fdatasync() return 0 on success or −1 if an error occurs, and set
errno to indicate
the error.
ERRORS
fsync and fdatasync fail if any of the following conditions are encountered:
[EBADF] fildes is not a valid descriptor.
[EINVAL] fildes refers to a file type to which
fsync() or fdatasync() does not apply.
WARNINGS
The current implementation of these functions is inefficient for large files.
AUTHOR
fsync() was developed by the University of California, Berkeley and HP.
SEE ALSO
fcntl(2), fcntl(5), open(2), select(2), sync(2), sync(1M), unistd(5).
STANDARDS CONFORMANCE
fsync(): AES, SVID3, XPG3, XPG4, POSIX.4
fdatasync():POSIX.4
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1