1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek and the American National Standards Committee X3, 6.\" on Information Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)fflush.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD: src/lib/libc/stdio/fflush.3,v 1.11 2007/01/09 00:28:06 imp Exp $ 34.\" 35.Dd December 23, 2017 36.Dt FFLUSH 3 37.Os 38.Sh NAME 39.Nm fflush , 40.Nm fpurge 41.Nd flush a stream 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In stdio.h 46.Ft int 47.Fn fflush "FILE *stream" 48.Ft int 49.Fn fpurge "FILE *stream" 50.Sh DESCRIPTION 51The function 52.Fn fflush 53forces a write of all buffered data for the given output or update 54.Fa stream 55via the stream's underlying write function. 56The open status of the stream is unaffected. 57.Pp 58If the 59.Fa stream 60argument is 61.Dv NULL , 62.Fn fflush 63flushes 64.Em all 65open output streams. 66.Pp 67The function 68.Fn fpurge 69erases any input or output buffered in the given 70.Fa stream . 71For output streams this discards any unwritten output. 72For input streams this discards any input read from the underlying object 73but not yet obtained via 74.Xr getc 3 ; 75this includes any text pushed back via 76.Xr ungetc 3 . 77.Sh RETURN VALUES 78Upon successful completion 0 is returned. 79Otherwise, 80.Dv EOF 81is returned and the global variable 82.Va errno 83is set to indicate the error. 84.Sh ERRORS 85.Bl -tag -width Er 86.It Bq Er EBADF 87The 88.Fa stream 89argument 90is not an open stream. 91.El 92.Pp 93The function 94.Fn fflush 95may also fail and set 96.Va errno 97for any of the errors specified for the routine 98.Xr write 2 , 99except that in case of 100.Fa stream 101being a read-only descriptor, 102.Fn fflush 103returns 0. 104.Sh SEE ALSO 105.Xr write 2 , 106.Xr fclose 3 , 107.Xr fopen 3 , 108.Xr setbuf 3 109.Sh STANDARDS 110The 111.Fn fflush 112function 113conforms to 114.St -isoC . 115