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分享寻求linux下将屏幕输出信息“同时”保存到文件中的方法
各位好！
我想将linux下屏幕输出信息同时保存到文件中，就是屏幕输出一行就保存到文件一行，而不是屏幕输出多行后文件中才有信息。不知道大家有什么方法么？
我现在用重定向的方法，出现的问题是屏幕输出多行后或者指令执行结束后，文件中才有信息，原因可能是保存到文件中时缓冲区不满不写入。
有遇到这种情况的么？怎么解决的？
谢谢大家。
我想将linux下屏幕输出信息同时保存到文件中，就是屏幕输出一行就保存到文件一行，而不是屏幕输出多行后文件中才有信息。不知道大家有什么方法么？
我现在用重定向的方法，出现的问题是屏幕输出多行后或者指令执行结束后，文件中才有信息，原因可能是保存到文件中时缓冲区不满不写入。
有遇到这种情况的么？怎么解决的？
谢谢大家。
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奋---斗 2013-12-09
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楼主你好，我现在越到一个跟你差不多的问题，是这样的，我的一个程序在后台运行，会时不时打印一些信息，我要记录这些信息该怎么做呢？后台程序不能修改，还望楼主帮帮忙
babihehe 2013-03-01
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不太会用这个，我也用来着
比如我执行./a.out，那么tee命令怎么用啊？
谢谢
babihehe 2013-03-01
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是这样的：
我调用linux下的一个工具包，它负责将执行的结果输出到屏幕上，它的输出是一行一行的连续输出
而我想将它输出的结果保存到文件中，当该屏幕上输出一行的时候，我也保存到文件中一行
但是现在的问题是，当屏幕输出了很多行或者输出了几行后该工具执行结束时，才有数据保存到文件中。
我不能控制该工具操作过程，这个时候怎么保存到文件好呢？fflush用在什么时候？
Franklin 2013-03-01
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tee
e.g.
make | tee make.log
图灵狗 2013-03-01
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1、不用重定向；
2、直接fflush(file)，file是你文件的句柄。
babihehe 2013-03-01
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fflush能作用于重定向输入输出流么？
如果不用重定向，那么有什么办法可以实时保存到文件么？
就是当屏幕输出一行的时候，文件也保存了一行，实现这个功能就行。谢谢
babihehe 2013-03-01
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不知道怎么手动刷新啊
用fflush么？
不知道怎么用才对
比如我用fflush（stdout）和fflush（stdin）都不能及时保存呢
难道我用的不对？
比如说执行ls命令，假设会显示n多行，那么我怎么刷新呢？
图灵狗 2013-03-01
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用fflush强制刷新，就会及时把缓冲区中的内容更新到文件中。
rocktyt 2013-03-01
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手动刷新缓冲即可
babihehe 2013-03-01
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谢谢各位的帮忙
分不多，谢谢大家啦
babihehe 2013-03-01
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嗯嗯，是的，现在我电脑上的缓存应该是4096
但是由于开发的软件在硬件平台上，好多东西可能都用到缓存，我也不敢修改缓存，怕有影响
最终这块功能修改了，以别的方式展示了
谢谢各位大哥了
现在结贴了
赵4老师 2013-03-01
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Linux下：
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 2013-03-01
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setvbuf
Controls stream buffering and buffer size.
int setvbuf( FILE *stream, char *buffer, int mode, size_t size );
Routine Required Header Compatibility
setvbuf <stdio.h> ANSI, Win 95, Win NT
For additional compatibility information, see Compatibility in the Introduction.
Libraries
LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version
Return Value
setvbuf returns 0 if successful, or a nonzero value if an illegal type or buffer size is specified.
Parameters
stream
Pointer to FILE structure
buffer
User-allocated buffer
mode
Mode of buffering
size
Buffer size in bytes. Allowable range: 2 < size < 32768. Internally, the value supplied for size is rounded down to the nearest multiple of 2.
Remarks
The setvbuf function allows the program to control both buffering and buffer size for stream. stream must refer to an open file that has not undergone an I/O operation since it was opened. The array pointed to by buffer is used as the buffer, unless it is NULL, in which case setvbuf uses an automatically allocated buffer of length size/2 * 2 bytes.
The mode must be _IOFBF, _IOLBF, or _IONBF. If mode is _IOFBF or _IOLBF, then size is used as the size of the buffer. If mode is _IONBF, the stream is unbuffered and size and buffer are ignored. Values for mode and their meanings are:
_IOFBF
Full buffering; that is, buffer is used as the buffer and size is used as the size of the buffer. If buffer is NULL, an automatically allocated buffer size bytes long is used.
_IOLBF
With MS-DOS, the same as _IOFBF.
_IONBF
No buffer is used, regardless of buffer or size.
Example
/* SETVBUF.C: This program opens two streams: stream1
* and stream2. It then uses setvbuf to give stream1 a
* user-defined buffer of 1024 bytes and stream2 no buffer.
*/
#include <stdio.h>
void main( void )
{
char buf[1024];
FILE *stream1, *stream2;
if( ((stream1 = fopen( "data1", "a" )) != NULL) &&
((stream2 = fopen( "data2", "w" )) != NULL) )
{
if( setvbuf( stream1, buf, _IOFBF, sizeof( buf ) ) != 0 )
printf( "Incorrect type or size of buffer for stream1\n" );
else
printf( "'stream1' now has a buffer of 1024 bytes\n" );
if( setvbuf( stream2, NULL, _IONBF, 0 ) != 0 )
printf( "Incorrect type or size of buffer for stream2\n" );
else
printf( "'stream2' now has no buffer\n" );
_fcloseall();
}
}
Output
'stream1' now has a buffer of 1024 bytes
'stream2' now has no buffer
Stream I/O Routines
See Also fclose, fflush, fopen, setbuf
赵4老师 2013-03-01
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楼主说的延迟显示问题可能需要设置标准输入输出的缓存大小为0
参考setbuf和setvbuf函数 ？
babihehe 2013-03-01
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试了，不行~~~
咋着办呢？
babihehe 2013-03-01
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因为我调用的工具，所以它输出命令的时候我不能控制
我修改了一下你的程序，起了一个线程，执行FOK那个函数
但是还是写不到文件中数据~~~~
小小小凯 2013-03-01
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用fflush(fp) fp文件描述符
babihehe 2013-03-01
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太厉害了~
你倒是提醒了我，自己写个保存屏幕信息的程序也挺好
不过，我得先研究研究你的代码
谢谢啦
赵4老师 2013-03-01
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我自己写的tee.c仅供参考：
#include <stdio.h>
#include <string.h>
FILE *f;
int c;
void main(int argc,char **argv) {
if (argc==3) {
if (stricmp(argv[1],"-a")) goto USAGE;
f=fopen(argv[2],"a");
if (NULL==f) goto FNULL;
goto FOK;
} else if (argc==2) {
if (0==strcmp(argv[1],"/?")) {
USAGE:
fprintf(stderr,"Usage: program | tee [-a] file\n");
return;
}
f=fopen(argv[1],"w");
if (NULL==f) goto FNULL;
FOK:
while (1) {
c=getchar();
if (EOF==c) break;
if (EOF==fputc(c,f)) {
putchar(c);
break;
} else {
if (EOF==putchar(c)) break;
}
}
fclose(f);
} else {
FNULL:
while (1) {
c=getchar();
if (EOF==c) break;
if (EOF==putchar(c)) break;
}
}
}
babihehe 2013-03-01
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嗯，我的应该有tee，因为我可以直接用这个命令
但是我用的时候也是有问题的，没用tee之前，执行结果很快就输出到屏幕上
加上tee之后，连屏幕输出都很慢了，而且是好几行一块出来，然后等好久又一块出来，大约4096个字节一起出来，不是原来一行一行的连续出来了，原来一行不到100个字节。
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