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FSYNC(2)		  FreeBSD System Calls Manual		      FSYNC(2)

NAME
     fdatasync,	fsync -- synchronise changes to	a file

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     fdatasync(int fd);

     int
     fsync(int fd);

DESCRIPTION
     The fsync() system	call causes all	modified data and attributes of	the
     file referenced by	the file descriptor fd 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.

     The fdatasync() system call causes	all modified data of fd	to be moved to
     a permanent storage device.  Unlike fsync(), the system call does not
     guarantee that file attributes or metadata	necessary to access the	file
     are committed to the permanent storage.

     The fsync() system	call should be used by programs	that require a file to
     be	in a known state, for example, in building a simple transaction	facil-
     ity.  If the file metadata	has already been committed, using fdatasync()
     can be more efficient than	fsync().

     Both fdatasync() and fsync() calls	are cancellation points.

RETURN VALUES
     The fsync() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     The fsync() and fdatasync() calls fail if:

     [EBADF]		The fd argument	is not a valid descriptor.

     [EINVAL]		The fd argument	refers to a socket, not	to a file.

     [EIO]		An I/O error occurred while reading from or writing to
			the file system.

SEE ALSO
     sync(2), syncer(4), sync(8)

HISTORY
     The fsync() system	call appeared in 4.2BSD.  The fdatasync() system call
     appeared in FreeBSD 11.1.

BUGS
     The fdatasync() system call currently does	not guarantee that enqueued
     aio(4) requests for the file referenced by	fd are completed before	the
     syscall returns.

FreeBSD	11.1			 May 24, 2017			  FreeBSD 11.1

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | BUGS

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