{{fbdoc item="title" value="FILEFLUSH"}}----
Flush application stream buffers to system, or system buffers to file

{{fbdoc item="syntax"}}##
	[[KeyPgDeclare|declare]] [[KeyPgFunction|function]] **""FileFlush""** ( [[KeyPgByval|byval]] //filenum// [[KeyPgAs|as]] [[KeyPgLong|long]] = -1, [[KeyPgByval|byval]] //systembuffers// [[KeyPgAs|as]] [[KeyPgLong|long]] = 0 ) [[KeyPgAs|as]] [[KeyPgLong|long]]
##
{{fbdoc item="usage"}}##
	#include "file.bi"
	//result// = **""FileFlush""**()
	//result// = **""FileFlush""**( //filenum// )
	//result// = **""FileFlush""**( //filenum//, //systembuffers// )
##
{{fbdoc item="param"}}
	##//filenum//##
		File number of bound file or device.  If not given, or -1, then flush all open files.
	##//systembuffers//##
		If non-zero, flush system buffers to physical device.  Default is zero (0).

{{fbdoc item="ret"}}
	Returns zero (0) for success or an error code if file buffers could not be flushed.

{{fbdoc item="desc"}}
	##**""FileFlush""**## writes application buffered output to the underlying stream, and if ##//systembuffers//## is non-zero, to the underlying physical device as well.
	
	In the form ##**""FileFlush(filenum)""**##, the application output buffer for a specific file are written.  And in the form ##**""FileFlush""**##, all application buffers are written to the system.  Typically, when a file is opened, the stream will be block buffered for ##binary## and ##random## files, and line buffered for ##append## and ##output## files.  The ##**""FileFlush""**## function overrides the normal buffering of the application and immediately writes buffered output to the system.  The system may have it's own buffers as well.
	
	In the form ##**""FileFlush(filenum,1)""**##, both the application buffer is flushed and the underlying system buffer is flushed to physical device.  In the form ##**""FileFlush(,1)""**##, all application buffers are flushed and all underlying system buffers are flushed to physical device.

{{fbdoc item="ex"}}
	{{fbdoc item="filename" value="examples/manual/fileio/fileflush.bas"}}%%(freebasic)
#include "file.bi"

Dim As Long f1, f2
Dim As String s

Print "File length", "File string"

f1 = Freefile
Open "fileflushtest.txt" For Output As #f1
Print #f1, "successful file flush"

f2 = Freefile
Open "fileflushtest.txt" For Input As #f2
Line Input #f2, s
Print Filelen("fileflushtest.txt"), "'" & s & "'"  '' the string is not yet physically written to the file

Fileflush(f1)
Line Input #f2, s
Print Filelen("fileflushtest.txt"), "'" & s & "'"  '' the string is now physically written to the file

Close #f2
Close #f1

Sleep
	%%Output (Windows):
		%%
File length   File string
 0            ''
 23           'successful file flush'
		%%
{{fbdoc item="diff"}}
	- New to ""FreeBASIC"".

{{fbdoc item="see"}}
	- ##[[KeyPgClose|Close]]##

{{fbdoc item="back" value="CatPgOpsys|Operating System Functions"}}