.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
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.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
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.\"     @(#)fflush.3	5.4 (Berkeley) 6/29/91
.\"
.\" Converted for Linux, Mon Nov 29 15:22:01 1993, faith@cs.unc.edu
.\"
.\" Modified 2000-07-22 by Nicol??s Lichtmaier <nick@debian.org>
.\" Modified 2001-10-16 by John Levon <moz@compsoc.man.ac.uk>
.\"
.TH FFLUSH 3  1993-11-29 "BSD MANPAGE" "Linux Programmer's Manual"
.SH NAME
fflush \- 刷新一个流
.SH "SYNOPSIS 总览"
.B #include <stdio.h>
.sp
.BI "int fflush(FILE *" stream );
.SH "DESCRIPTION 描述"
函数
.B fflush
强制在所给的输出流或更新流
.I stream
上，写入在用户空间缓冲的所有数据，使用流的底层写功能函数。流的打开状态不受影响。
.PP
如果参数
.I stream
是
.BR NULL ,
.B fflush
刷新
.I 所有
打开的流。
.PP
要使用非锁定的对应版本，参见
.BR unlocked_stdio (3)
。
.SH "RETURN VALUE 返回值"
成功执行返回 0，否则返回
.B EOF
并设置全局变量
.I errno
来指示错误发生。
.SH ERRORS
.TP
.B EBADF
.I Stream
不是一个打开的流，或者不是用于输出。
.PP
函数
.B fflush
也可能失败并置
.I errno
为
.BR write (2)
指定的值。
.SH "NOTES 要点"
注意
.B fflush()
仅仅刷新用户空间的由 C 库提供的缓冲。要保证数据被物理地存储到磁盘上，必须也刷新内核缓冲。例如，使用
.BR sync (2)
或
.BR fsync (2).
.SH "CONFORMING TO 标准参考"
函数
.BR fflush()
遵循 ANSI X3.159-1989 (``ANSI C'') 标准。
.SH "SEE ALSO 参见"
.BR fsync (2),
.BR sync (2),
.BR write (2),
.BR fclose (3),
.BR fopen (3),
.BR setbuf (3),
.BR unlocked_stdio (3)