Libc-1353.11.2.tar.gz

[apple/libc.git] / stdio / FreeBSD / fflush.3

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.\"     @(#)fflush.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/stdio/fflush.3,v 1.11 2007/01/09 00:28:06 imp Exp $
.\"
.Dd August 1, 2019
.Dt FFLUSH 3
.Os
.Sh NAME
.Nm fflush ,
.Nm fpurge
.Nd flush a stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.Ft int
.Fn fflush "FILE *stream"
.Ft int
.Fn fpurge "FILE *stream"
.Sh DESCRIPTION
The function
.Fn fflush
synchronizes the state of the given
.Fa stream
in light of buffered I/O.
For output or update streams it writes all buffered data via the stream's
underlying write function.
For input streams it seeks to the current file position indicator via the
stream's underlying seek function.
The open status of the stream is unaffected.
.Pp
If the
.Fa stream
argument is
.Dv NULL ,
.Fn fflush
flushes
.Em all
open streams.
.Pp
The function
.Fn fpurge
erases any input or output buffered in the given
.Fa stream .
For output streams this discards any unwritten output.
For input streams this discards any input read from the underlying object
but not yet obtained via
.Xr getc 3 ;
this includes any text pushed back via
.Xr ungetc 3 .
.Sh RETURN VALUES
Upon successful completion 0 is returned.
Otherwise,
.Dv EOF
is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa stream
argument
is not an open stream.
.El
.Pp
The function
.Fn fflush
may also fail and set
.Va errno
for any of the errors specified for the routines
.Xr write 2
and
.Xr lseek 2 .
.Sh SEE ALSO
.Xr write 2 ,
.Xr fclose 3 ,
.Xr fopen 3 ,
.Xr lseek 2 ,
.Xr setbuf 3
.Sh STANDARDS
The
.Fn fflush
function
conforms to
.St -isoC
and
.St -susv3 .