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分享哪些情况下会刷新输入缓冲区？
哪些情况下会刷新输入缓冲区？
1：输入缓冲区满的时候。
2：cin.sync()等刷新输入缓冲区的操作。
3:程序正常结束的时候。
还有什么时候会刷新输入缓冲区？请高手来指教。
1：输入缓冲区满的时候。
2：cin.sync()等刷新输入缓冲区的操作。
3:程序正常结束的时候。
还有什么时候会刷新输入缓冲区？请高手来指教。
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李刚弄死他 2013-09-22
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请看清题目，这里是刷新输入缓冲区，你的rewind(stdin)是不标准的方法，只能用在windows系统中，linux用这个方法就是错误的，输入缓冲区不会被刷新。另外，第2条：cin.sync()等刷新输入缓冲区的操作。这个“等”字你应该是了解的吧，它包括cin.ignore()等其他刷新输入缓冲区的操作， 也包括你那个非标准方法rewind(stdin)。
turing-complete 2013-09-22
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赵4老师 2013-09-22
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你让闭就闭啊！？
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\rewind.c" 2 occurrences found on 2 lines
53: _flush(stream);
60: /* [note: _flush set _cnt=0 and _ptr=_base] */
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\setvbuf.c" 1 occurrences found on 1 lines
87: _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\_sftbuf.c" 2 occurrences found on 2 lines
112: * If stdout/stderr is being buffered and it is a device, _flush and
151: _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fclose.c" 2 occurrences found on 2 lines
33: * returns 0 if OK, EOF if fails (can't _flush, not a FILE, not open, etc.)
103: result = _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fflush.c" 4 occurrences found on 4 lines
104: if (_flush(str) != 0) {
105: /* _flush failed, don't attempt to commit */
120: *int _flush(stream) - flush the buffer on a single stream
139: int __cdecl _flush (
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fseek.c" 1 occurrences found on 1 lines
162: _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fseeki64.c" 1 occurrences found on 1 lines
125: _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fwrite.c" 2 occurrences found on 2 lines
151: buffer, it must be full so _flush it. */
154: if (_flush(stream)) {
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\internal.h" 1 occurrences found on 1 lines
363: int __cdecl _flush(_Inout_ FILE * _File);
赵4老师 2013-09-22
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请闭嘴，谢谢合作。[/quote]
你让闭就闭啊！
[code=c]File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\rewind.c" 2 occurrences found on 2 lines
53: _flush(stream);
60: /* [note: _flush set _cnt=0 and _ptr=_base] */
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\setvbuf.c" 1 occurrences found on 1 lines
87: _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\_sftbuf.c" 2 occurrences found on 2 lines
112: * If stdout/stderr is being buffered and it is a device, _flush and
151: _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fclose.c" 2 occurrences found on 2 lines
33: * returns 0 if OK, EOF if fails (can't _flush, not a FILE, not open, etc.)
103: result = _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fflush.c" 4 occurrences found on 4 lines
104: if (_flush(str) != 0) {
105: /* _flush failed, don't attempt to commit */
120: *int _flush(stream) - flush the buffer on a single stream
139: int __cdecl _flush (
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fseek.c" 1 occurrences found on 1 lines
162: _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fseeki64.c" 1 occurrences found on 1 lines
125: _flush(stream);
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\fwrite.c" 2 occurrences found on 2 lines
151: buffer, it must be full so _flush it. */
154: if (_flush(stream)) {
File: "C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\internal.h" 1 occurrences found on 1 lines
363: int __cdecl _flush(_Inout_ FILE * _File);
李刚弄死他 2013-09-22
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请闭嘴，谢谢合作。
赵4老师 2013-09-22
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rewind(stdin);
先
http://www.microsoft.com/visualstudio/chs/downloads#d-2010-express
点开Visual C++ 2010 Express下面的语言选‘简体中文’，再点立即安装
再参考C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\*.*
max_min_ 2013-09-22
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你说的是刷新输出缓冲区，这里是输入，请仔细看题目。[/quote]
sorry!
李刚弄死他 2013-09-22
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另外，第1条有错误，遇到"\n"并不会刷新缓冲区。
李刚弄死他 2013-09-22
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你说的是刷新输出缓冲区，这里是输入，请仔细看题目。
max_min_ 2013-09-22
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一般情况下：
1 遇到"\n"换行结束符
2 fflush强制刷新缓冲区
3 缓冲区满了也会刷新
4 程序结束了，
李刚弄死他 2013-09-22
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大家来分析一下。
李刚弄死他 2013-09-22
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无言。
赵4老师 2013-09-22
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不要迷信书、考题、老师、回帖；
要迷信CPU、编译器、调试器、运行结果。
并请结合“盲人摸太阳”和“驾船出海时一定只带一个指南针。”加以理解。
任何理论、权威、传说、真理、标准、解释、想象、知识……都比不上摆在眼前的事实！
试问帖主本人符合哪些条“人”的标准？
1+1=2这条标准什么时候被严格符合过？
醒醒吧，标准控们！
李刚弄死他 2013-09-22
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MSDN不是标准，OK，请参阅C89标准，谢谢。
赵4老师 2013-09-22
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SETBUF
Section: Linux Programmer's Manual (3 )
Updated: 2001-06-09
--------------------------------------------------------------------------------
NAME
setbuf, setbuffer, setlinebuf, setvbuf - stream buffering operations
SYNOPSIS
#include <stdio.h>
void setbuf(FILE *stream, char *buf);
void setbuffer(FILE *stream, char *buf, size_t size);
void setlinebuf(FILE *stream);
int setvbuf(FILE *stream, char *buf, int mode , size_t size);
DESCRIPTION
The three types of buffering available are unbuffered, block buffered, and line buffered. When an output stream is unbuffered, information appears on the destination file or terminal as soon as written; when it is block buffered many characters are saved up and written as a block; when it is line buffered characters are saved up until a newline is output or input is read from any stream attached to a terminal device (typically stdin). The function fflush(3) may be used to force the block out early. (See fclose(3).) Normally all files are block buffered. When the first I/O operation occurs on a file, malloc(3) is called, and a buffer is obtained. If a stream refers to a terminal (as stdout normally does) it is line buffered. The standard error stream stderr is always unbuffered by default.
The setvbuf function may be used on any open stream to change its buffer. The mode parameter must be one of the following three macros:
_IONBF
unbuffered
_IOLBF
line buffered
_IOFBF
fully buffered
Except for unbuffered files, the buf argument should point to a buffer at least size bytes long; this buffer will be used instead of the current buffer. If the argument buf is NULL, only the mode is affected; a new buffer will be allocated on the next read or write operation. The setvbuf function may only be used after opening a stream and before any other operations have been performed on it.
The other three calls are, in effect, simply aliases for calls to setvbuf. The setbuf function is exactly equivalent to the call
setvbuf(stream, buf, buf ? _IOFBF : _IONBF, BUFSIZ);
The setbuffer function is the same, except that the size of the buffer is up to the caller, rather than being determined by the default BUFSIZ. The setlinebuf function is exactly equivalent to the call:
setvbuf(stream, (char *)NULL, _IOLBF, 0);
RETURN VALUE
The function setvbuf returns 0 on success. It can return any value on failure, but returns nonzero when mode is invalid or the request cannot be honoured. It may set errno on failure. The other functions are void.
CONFORMING TO
The setbuf and setvbuf functions conform to ANSI X3.159-1989 (``ANSI C'').
BUGS
The setbuffer and setlinebuf functions are not portable to versions of BSD before 4.2BSD, and are available under Linux since libc 4.5.21. On 4.2BSD and 4.3BSD systems, setbuf always uses a suboptimal buffer size and should be avoided. You must make sure that both buf and the space it points to still exist by the time stream is closed, which also happens at program termination. For example, the following is illegal:
#include <stdio.h>
int main()
{
char buf[BUFSIZ];
setbuf(stdin, buf);
printf("Hello, world!\n");
return 0;
}
SEE ALSO
fclose(3), fflush(3), fopen(3), fread(3), malloc(3), printf(3), puts(3)
--------------------------------------------------------------------------------
赵4老师 2013-09-22
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MSDN:fopen
...
When the "r+", "w+", or "a+" access type is specified, both reading and writing are allowed (the file is said to be open for “update”). However, when you switch between reading and writing, there must be an intervening fflush, fsetpos, fseek, or rewind operation. The current position can be specified for the fsetpos or fseek operation, if desired.
...
--------------------------------------------------------------------------------
FOPEN
Section: Linux Programmer's Manual (3 )
Updated: 2002-01-03
NAME
fopen, fdopen, freopen - stream open functions
SYNOPSIS
#include <stdio.h>
FILE *fopen(const char *path, const char *mode);
FILE *fdopen(int fildes, const char *mode);
FILE *freopen(const char *path, const char *mode, FILE *stream);
DESCRIPTION
Reads and writes may be intermixed on read/write streams in any order. Note that ANSI C requires that a file positioning function intervene between output and input, unless an input operation encounters end-of-file. (If this condition is not met, then a read is allowed to return the result of writes other than the most recent.) Therefore it is good practice (and indeed sometimes necessary under Linux) to put an fseek or fgetpos operation between write and read operations on such a stream. This operation may be an apparent no-op (as in fseek(..., 0L, SEEK_CUR) called for its synchronizing side effect.
李刚弄死他 2013-09-22
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fflush也是这样，对于输入流是未定义的行为。setvbuf仅仅用来设置缓冲区为无缓冲，并不能执行刷新的功能，fclose实际上调用了flush函数，起到刷新作用的是flush，而不是它，因此它不能算入。fseek和fwrite更是风马牛不相及。因此， 再次说一遍，请闭嘴，谢谢。
李刚弄死他 2013-09-22
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rewind只在微软的操作系统下可以有刷新输入/输出缓冲区的作用，在其他操作系统下，仅仅有刷新输出缓冲区的作用，即该函数对输入流是未定义的行为，请参阅C89标准。
赵4老师 2013-09-22
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FSEEK
Section: Linux Programmer's Manual (3 )
Updated: 1993-11-29
--------------------------------------------------------------------------------
NAME
fgetpos, fseek, fsetpos, ftell, rewind - reposition a stream
SYNOPSIS
#include <stdio.h>
int fseek(FILE *stream, long offset, int whence);
long ftell(FILE *stream);
void rewind(FILE *stream);
int fgetpos(FILE *stream, fpos_t *pos);
int fsetpos(FILE *stream, fpos_t *pos);
DESCRIPTION
The fseek function sets the file position indicator for the stream pointed to by stream. The new position, measured in bytes, is obtained by adding offset bytes to the position specified by whence. If whence is set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the start of the file, the current position indicator, or end-of-file, respectively. A successful call to the fseek function clears the end-of-file indicator for the stream and undoes any effects of the ungetc(3) function on the same stream.
The ftell function obtains the current value of the file position indicator for the stream pointed to by stream.
The rewind function sets the file position indicator for the stream pointed to by stream to the beginning of the file. It is equivalent to:
(void)fseek(stream, 0L, SEEK_SET)
except that the error indicator for the stream is also cleared (see clearerr(3)).
The fgetpos and fsetpos functions are alternate interfaces equivalent to ftell and fseek (with whence set to SEEK_SET), setting and storing the current value of the file offset into or from the object referenced by pos. On some non-UNIX systems an fpos_t object may be a complex object and these routines may be the only way to portably reposition a text stream.
RETURN VALUE
The rewind function returns no value. Upon successful completion, fgetpos, fseek, fsetpos return 0, and ftell returns the current offset. Otherwise, -1 is returned and the global variable errno is set to indicate the error.
ERRORS
EBADF
The stream specified is not a seekable stream.
EINVAL
The whence argument to fseek was not SEEK_SET, SEEK_END, or SEEK_CUR.
The function fgetpos, fseek, fsetpos, and ftell may also fail and set errno for any of the errors specified for the routines fflush(3), fstat(2), lseek(2), and malloc(3).
CONFORMING TO
The fgetpos, fsetpos, fseek, ftell, and rewind functions conform to ANSI X3.159-1989 (``ANSI C'').
SEE ALSO
lseek(2), fseeko(3)
--------------------------------------------------------------------------------
赵4老师 2013-09-22
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由15楼搜索结果可以看出：
rewind,setvbuf,fflush,fclose,fseek,fwrite时会刷新输入/输出缓冲区。
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