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 permanent 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.
STANDARDS CONFORMANCE
fsync(): AES, SVID3, XPG3, XPG4, POSIX.4
fdatasync(): POSIX.4
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