DOS Fn 68H: Commit File
Expects: AH 68H
BX file handle of file to flush
Returns: AX error code if CF is set to CY
Info: This function forces DOS to flush its RAM buffers of file data
for the selected file handle.
DOS normally avoids disk I/O by writing data to RAM buffers until
a sector is full or the file is closed. This provides a way to
force DOS to write the buffered data to disk.
Versions: ■ Prior to DOS 3.3, you can force a file flush by closing, then
reopening the file. But by using fn 45H to duplicate the
handle and then close the duplicate.
■ Starting with DOS 4.0, you can force a flush on each write by
opening the file via fn 6cH (extended file open/create).
Notes: ■ This does NOT flush the Smartdrv cache buffers (the data may
sit in memory for a few seconds). You can force Smartdrv to
write all data by using fn 0dH (reset disk).
See Also: Handle-Oriented File I/O