136 lines
3.7 KiB
Groff
136 lines
3.7 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek and the American National Standards Committee X3,
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.\" on Information Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)fflush.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd May 1, 2020
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.Dt FFLUSH 3
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.Os
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.Sh NAME
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.Nm fflush ,
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.Nm fflush_unlocked ,
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.Nm fpurge
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.Nd flush a stream
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdio.h
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.Ft int
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.Fn fflush "FILE *stream"
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.Ft int
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.Fn fflush_unlocked "FILE *stream"
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.Ft int
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.Fn fpurge "FILE *stream"
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.Sh DESCRIPTION
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The function
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.Fn fflush
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forces a write of all buffered data for the given output or update
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.Fa stream
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via the stream's underlying write function.
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The open status of the stream is unaffected.
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.Pp
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If the
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.Fa stream
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argument is
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.Dv NULL ,
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.Fn fflush
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flushes
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.Em all
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open output streams.
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.Pp
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The
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.Fn fflush_unlocked
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function is equivalent to
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.Fn fflush ,
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except that the caller is responsible for locking the stream with
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.Xr flockfile 3
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before calling it.
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This function may be used to avoid the overhead of locking the stream and to
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prevent races when multiple threads are operating on the same stream.
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.Pp
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The function
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.Fn fpurge
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erases any input or output buffered in the given
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.Fa stream .
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For output streams this discards any unwritten output.
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For input streams this discards any input read from the underlying object
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but not yet obtained via
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.Xr getc 3 ;
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this includes any text pushed back via
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.Xr ungetc 3 .
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.Sh RETURN VALUES
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Upon successful completion 0 is returned.
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Otherwise,
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.Dv EOF
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is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa stream
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argument
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is not an open stream.
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.El
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.Pp
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The function
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.Fn fflush
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may also fail and set
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.Va errno
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for any of the errors specified for the routine
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.Xr write 2 ,
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except that in case of
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.Fa stream
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being a read-only descriptor,
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.Fn fflush
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returns 0.
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.Sh SEE ALSO
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.Xr write 2 ,
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.Xr fclose 3 ,
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.Xr fopen 3 ,
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.Xr setbuf 3
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.Sh STANDARDS
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The
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.Fn fflush
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function
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conforms to
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.St -isoC .
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.Sh HISTORY
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The
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.Fn fflush
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function first appeared in
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.At v4 .
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The
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.Fn fpurge
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function first appeared in
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.Bx 4.4 .
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