fsync - synchronize changes to file

Syntax	#include <unistd.h> int fsync(int fildes);
Description	fsync() causes all the modified data and attributes of fildes that are still in the buffer to bewritten to the physical storage medium.
Return val.	0 -1	if successful if an error occurs; errno is set to indicate the error.
Errors	fsync() will fail if:
	EBADF	fildes is not a valid file descriptor.
	EINTR	A signal was caught during the fsync() system call.
	EINVAL	fildes refers to a file on which this operation is not possible. An attempt was made to access a BS2000 file.
	EIO	An I/O error occurred while reading from or writing to the file system.
Notes	fsync() should be used by programs which require modifications to a file to be completed before continuing; for example, a program which contains a simple transaction facility might use it to ensure that all modifications to a file or files caused by a transaction are recorded. fsync() is executed only for POSIX files.
See also	unistd.h.